Would a bat familiar have a passive perception of 16 in most cases?

In its stat block a bat is shown to have a passive perception of 11; the standard 10 plus wisdom. However, the bats ability Echolocation states that it "can’t use its blindsight while deafened", which heavily implies that the bat relies on hearing for detection. This married with its other ability Keen Hearing which says that a bat has "advantage on Wisdom (Perception) checks that rely on hearing" and the knowledge that advantage on perception checks also translates to a +5 to passive perception makes me think that barring special cases (such as perception checks that rely on detecting a certain smell), a bat should be treated as having a passive perception of 16.

Is this correct, or is there a reason a bats perception would stay at 11?