Appears that udev isn't detecting removal. Suspect this is because the device gets unbound from the kernel and taken over by the usb module.
Here's an example of plug-unplug
KERNEL[1550.466276] add /devices/platform/soc/20980000.usb/usb1/1-1/1-1.3/1-1.3.4 (usb)
KERNEL[1550.476696] add /devices/platform/soc/20980000.usb/usb1/1-1/1-1.3/1-1.3.4/1-1.3.4:1.0 (usb)
KERNEL[1550.482847] add /devices/platform/soc/20980000.usb/usb1/1-1/1-1.3/1-1.3.4/1-1.3.4:1.0/ttyUSB0 (usb-serial)
KERNEL[1550.483329] add /devices/platform/soc/20980000.usb/usb1/1-1/1-1.3/1-1.3.4/1-1.3.4:1.0/ttyUSB0/tty/ttyUSB0 (tty)
KERNEL[1550.483686] bind /devices/platform/soc/20980000.usb/usb1/1-1/1-1.3/1-1.3.4/1-1.3.4:1.0/ttyUSB0 (usb-serial)
KERNEL[1550.484164] bind /devices/platform/soc/20980000.usb/usb1/1-1/1-1.3/1-1.3.4/1-1.3.4:1.0 (usb)
KERNEL[1550.484772] bind /devices/platform/soc/20980000.usb/usb1/1-1/1-1.3/1-1.3.4 (usb)
UDEV [1551.544487] add /devices/platform/soc/20980000.usb/usb1/1-1/1-1.3/1-1.3.4 (usb)
UDEV [1551.816866] add /devices/platform/soc/20980000.usb/usb1/1-1/1-1.3/1-1.3.4/1-1.3.4:1.0 (usb)
KERNEL[1551.836990] remove /devices/platform/soc/20980000.usb/usb1/1-1/1-1.3/1-1.3.4/1-1.3.4:1.0/ttyUSB0/tty/ttyUSB0 (tty)
KERNEL[1551.840431] unbind /devices/platform/soc/20980000.usb/usb1/1-1/1-1.3/1-1.3.4/1-1.3.4:1.0/ttyUSB0 (usb-serial)
KERNEL[1551.845881] remove /devices/platform/soc/20980000.usb/usb1/1-1/1-1.3/1-1.3.4/1-1.3.4:1.0/ttyUSB0 (usb-serial)
KERNEL[1551.853183] unbind /devices/platform/soc/20980000.usb/usb1/1-1/1-1.3/1-1.3.4/1-1.3.4:1.0 (usb)
KERNEL[1551.853745] remove /devices/platform/soc/20980000.usb/usb1/1-1/1-1.3/1-1.3.4/1-1.3.4:1.0 (usb)
KERNEL[1551.863523] unbind /devices/platform/soc/20980000.usb/usb1/1-1/1-1.3/1-1.3.4 (usb)
KERNEL[1551.871341] bind /devices/platform/soc/20980000.usb/usb1/1-1/1-1.3/1-1.3.4 (usb)
UDEV [1551.968520] add /devices/platform/soc/20980000.usb/usb1/1-1/1-1.3/1-1.3.4/1-1.3.4:1.0/ttyUSB0 (usb-serial)
UDEV [1552.056426] add /devices/platform/soc/20980000.usb/usb1/1-1/1-1.3/1-1.3.4/1-1.3.4:1.0/ttyUSB0/tty/ttyUSB0 (tty)
UDEV [1552.220543] bind /devices/platform/soc/20980000.usb/usb1/1-1/1-1.3/1-1.3.4/1-1.3.4:1.0/ttyUSB0 (usb-serial)
UDEV [1552.295971] bind /devices/platform/soc/20980000.usb/usb1/1-1/1-1.3/1-1.3.4/1-1.3.4:1.0 (usb)
UDEV [1552.396499] bind /devices/platform/soc/20980000.usb/usb1/1-1/1-1.3/1-1.3.4 (usb)
UDEV [1552.451450] remove /devices/platform/soc/20980000.usb/usb1/1-1/1-1.3/1-1.3.4/1-1.3.4:1.0/ttyUSB0/tty/ttyUSB0 (tty)
UDEV [1552.527288] unbind /devices/platform/soc/20980000.usb/usb1/1-1/1-1.3/1-1.3.4/1-1.3.4:1.0/ttyUSB0 (usb-serial)
UDEV [1552.548201] remove /devices/platform/soc/20980000.usb/usb1/1-1/1-1.3/1-1.3.4/1-1.3.4:1.0/ttyUSB0 (usb-serial)
UDEV [1552.576451] unbind /devices/platform/soc/20980000.usb/usb1/1-1/1-1.3/1-1.3.4/1-1.3.4:1.0 (usb)
UDEV [1552.599482] remove /devices/platform/soc/20980000.usb/usb1/1-1/1-1.3/1-1.3.4/1-1.3.4:1.0 (usb)
UDEV [1552.647279] unbind /devices/platform/soc/20980000.usb/usb1/1-1/1-1.3/1-1.3.4 (usb)
UDEV [1552.738097] bind /devices/platform/soc/20980000.usb/usb1/1-1/1-1.3/1-1.3.4 (usb)
KERNEL[1601.756409] unbind /devices/platform/soc/20980000.usb/usb1/1-1/1-1.3/1-1.3.4 (usb)
KERNEL[1601.759204] remove /devices/platform/soc/20980000.usb/usb1/1-1/1-1.3/1-1.3.4 (usb)
UDEV [1602.279535] unbind /devices/platform/soc/20980000.usb/usb1/1-1/1-1.3/1-1.3.4 (usb)
UDEV [1602.296272] remove /devices/platform/soc/20980000.usb/usb1/1-1/1-1.3/1-1.3.4 (usb)
And the corresponding journalctl result:
Jul 14 22:06:05 HUSK systemd[1]: Started usbip@1-1.3.4.service - USB/IP share usb device on given usb port 1-1.3.4; called by device specific udev rule.
Jul 14 22:06:06 HUSK sh[798]: usbip: info: bind device on busid 1-1.3.4: complete
Jul 14 22:22:10 HUSK systemd[1]: Stopping usbip@1-1.3.4.service - USB/IP share usb device on given usb port 1-1.3.4; called by device specific udev rule...
Jul 14 22:22:10 HUSK sh[1073]: usbip: error: device is not bound to usbip-host driver
Jul 14 22:22:10 HUSK systemd[1]: usbip@1-1.3.4.service: Deactivated successfully.
Jul 14 22:22:10 HUSK systemd[1]: Stopped usbip@1-1.3.4.service - USB/IP share usb device on given usb port 1-1.3.4; called by device specific udev rule.
Jul 14 22:22:10 HUSK systemd[1]: Started usbip@1-1.3.4.service - USB/IP share usb device on given usb port 1-1.3.4; called by device specific udev rule.
Jul 14 22:22:10 HUSK sh[1075]: usbip: info: bind device on busid 1-1.3.4: complete
Jul 14 22:26:44 HUSK systemd[1]: Stopping usbip@1-1.3.4.service - USB/IP share usb device on given usb port 1-1.3.4; called by device specific udev rule...
Jul 14 22:26:44 HUSK sh[1113]: usbip: error: device is not bound to usbip-host driver
Jul 14 22:26:44 HUSK systemd[1]: usbip@1-1.3.4.service: Deactivated successfully.
Jul 14 22:26:44 HUSK systemd[1]: Stopped usbip@1-1.3.4.service - USB/IP share usb device on given usb port 1-1.3.4; called by device specific udev rule.
Jul 14 22:26:44 HUSK systemd[1]: Started usbip@1-1.3.4.service - USB/IP share usb device on given usb port 1-1.3.4; called by device specific udev rule.
Jul 14 22:26:44 HUSK sh[1117]: usbip: info: bind device on busid 1-1.3.4: complete
Jul 14 22:28:32 HUSK systemd[1]: Stopping usbip@1-1.3.4.service - USB/IP share usb device on given usb port 1-1.3.4; called by device specific udev rule...
Jul 14 22:28:32 HUSK sh[1147]: usbip: error: device with the specified bus ID does not exist
Jul 14 22:28:32 HUSK systemd[1]: usbip@1-1.3.4.service: Deactivated successfully.
Jul 14 22:28:32 HUSK systemd[1]: Stopped usbip@1-1.3.4.service - USB/IP share usb device on given usb port 1-1.3.4; called by device specific udev rule.
Jul 14 22:28:49 HUSK systemd[1]: Started usbip@1-1.3.4.service - USB/IP share usb device on given usb port 1-1.3.4; called by device specific udev rule.
Jul 14 22:28:49 HUSK sh[1156]: usbip: info: bind device on busid 1-1.3.4: complete
Appears that udev isn't detecting removal. Suspect this is because the device gets unbound from the kernel and taken over by the usb module.
Here's an example of plug-unplug
And the corresponding journalctl result: