Reduce the claims about every block

They are not absolutely true.

Signed-off-by: mulhern <amulhern@redhat.com>

Author: mulkieran

docs/stratis.txt

@@ -118,16 +118,13 @@ pool unbind <(clevis|keyring)> <pool name> [--token-slot <token slot>]::
      the "pool encryption" subcommand. The "pool unbind" subcommand that you
      are using now is deprecated and will be removed in stratis 3.10.0.
 pool encryption on --in-place <(--uuid <uuid> |--name <name>)> [--key-desc <key_desc>] [--clevis <(nbde|tang|tpm2)> [--tang-url <tang_url>] [<(--thumbprint <thp> | --trust-url)>]::
-     Turn encryption on for the specified pool. This operation must encrypt
-     every block in the pool and takes time proportional to the size of the
-     pool.
+     Turn encryption on for the specified pool. This operation takes time
+     proportional to the size of the pool.
 pool encryption off --in-place <(--uuid <uuid> |--name <name>)>::
-     Turn encryption off for the specified pool. This operation must write
-     the plain text of every block in the pool and takes time proportional to
-     the size of the pool.
+     Turn encryption off for the specified pool. This operation takes time
+     proportional to the size of the pool.
 pool encryption reencrypt --in-place <(--uuid <uuid> |--name <name>)>::
-     Reencrypt the pool with a new master key. This operation must overwrite
-     every block in the pool with re-encrypted data and takes time
+     Reencrypt the pool with a new master key. This operation takes time
      proportional to the size of the pool.
 pool encryption bind <(nbde|tang)> <(--uuid <uuid> |--name <name>)> <(--thumbprint <thp> | --trust-url)> <url>::
      Bind the devices in the specified pool to a supplementary encryption
@@ -275,9 +272,9 @@ OPTIONS
         For V2 pools only. Use the token slot number to select among
         different bindings that use the same encryption method.
 --in-place ::
-        This is a mandatory option that must be set when requesting
-        a long-running in-place encryption operation. These operations are
-        a kind that must read and write every block in the pool. Hence these
+        This is a mandatory option that must be set when requesting a
+        long-running in-place encryption operation. These operations are a
+        kind that change the pool's data as well as its metadata. Hence these
         operations take a time that is linear in the size of the pool.
         Additionally, these operations are run in place, that is, the
         pool's data blocks are directly modified while it is in use. While