It seems to me like libewf will not discover files inside of L01 images created by FEX Imager. Sample L01 file zipped and attached (small_fex_test.zip) -- the L01 has just a single text file inside.
Discovered this because Autopsy also doesn't find these files, and seems to throw no errors. I think this might extend to any files created by FEX Imager, but I didn't do extensive testing.