Understands, But Can't Speak

[Psyren]

one good example may be kenku. they lack the creativity to speak on their own because they were cursed. they cannot create their own thoughts from scratch. So I'd say they don't write or talk but can read and mimic. maybe even read aloud cause it is not their thoughts.

FYI, they've been errata'ed to remove this limitation, so even if they couldn't write or talk on their own before they definitely can now.