Many blocks in the game have segmented collision bounds, which give them more detailed interactions. The lectern has an angled top, which is represented in its hitbox by a stairstep pattern. however, this angled section of its model is not present in its collision at all, and you can stand inside of it freely.
Linked issues
duplicates 1
Attachments
Comments 3
It's actually a duplicate of MC-142044
I don't see how this is a duplicate, as the other report was simply suggesting changing the model, whereas this report points out the difference between model, hitbox, and collision, which most multi-segment blocks don't have, making this an inconsistency.