Except for a few weirdos base = 1 is kind of the norm 😉
(I do understand your use case -- I do that too although probably less often than you seem to. But it is helpful to verify that ProTop is behaving as expected.)
As Paul says every block with data in it must be read - even for an incremental backup. Which is why an incremental backup takes about as long to run as a full backup.
-Bp 10 helps to prevent the entire -B buffer pool getting flushed as a result of a backup running and the follow-on impact that that will have to the hit ratio. During the backup itself though you will still almost certainly see a poor hit ratio.
