The DBCC will not raise an exception but only messages ("informative"), so the TRY/CATCH will not prevent anything (and so the 'return' statement will not be reach).

The Backup not fully verify integrity of database structure, just collect everything 'as it' and dump in bak file.

Which are the cases/limits/frontiers between success or fail in backup process over a corrupted db ?

edit: correct a false assert and so adjust the question 😉