Mobs that can shoot arrows with a bow can run very fast, even when walking on honey blocks they don't get slowed down. Instead of strafing (walking backwards slowly), they run towards their targets and spin around them until they have already killed their targets. This can be tested even without using a flat world that generates with honey blocks.
Affected mobs
Skeletons
Strays
Illusioners
Wither skeletons armed with bows
OTHER
Any entity that has a skeleton/stray/wither skeleton or illusioner as a passenger also runs very fast, ignoring the slowness effect of the honey block.
Linked issues
Attachments
Comments
Probably related to that issue.

Duplicate of MC-104900 (happens on most blocks with a non-standard height).
Same issue as MC-157645?