I don't know who started it, but there was an extremely popular, kind of bougie recipe from something like NYT cooking or Bon Appetit a while ago that called for a whole banana, split down the middle and pressed into the top as a sort of avant garde garnish (e.g. here). It's not the worst, but it doesn't really add anything to the flavour or texture.

I'm guessing that a bunch of lesser recipe developers took that trend and ran it into the ground, so people are now just shoving whole bananas into their bread and trying to make it work.