Standing on entities with solid collision boxes (shulkers, boats) kicks you for flying

The bug

If you stand on a shulker while it's "expanding" upwards (not sure how to describe it), you will get kicked: "Flying is not enabled on this server".

How to reproduce

1. Summon a shulker
2. Go invisible
3. Stand on the shulker
4. Wait 5 seconds

Note: can be only reproduced on a server with allow-flight=false

Affected situations

• Standing on open shulkers
• Riding a boat that is floating on an entity (see MC-96499)
• Affects standing on a boat as well, see MC-105652

Situations in which it could happen

• Flying upwards with elytra
• Jump boost
• Explosions
• Dragon wing attack