The bug
Despite being large enough to fit, bees cannot find their way through a hole created by four stairs put together (see pictures).
Linked issues
relates to 2
Attachments
Comments 11
MC-21109 covers that for other mobs
Can confirm. Related to MC-159724.
1 more comments
Not just bees! In 1.16 Pre 3 this also applies to all other smaller mobs who could logically fit through, such as chickens, silverfish, wolves, etc.
It's not even treated like any kind of opening to any mob.