Spawn egg spawned Cats act like Ocelots

Can confirm.

Might be intended, only the CatType value is changed, OwnerUUID stays unchanged.

Tame cat would change its skin.

Then the bug is rather "Cat spawned with spawn egg does not have OwnerUUID value of player using the spawn egg". I am not sure however what would happen when you use the id "Cat" in commands. Having the player executing the command becoming the owner would be awesome though.

I am not sure however what would happen when you use the id "Cat" in commands.

You can't it's an alias, it can't be targeted with selectors or /summoned at the moment. (unknown if intended)

You can use it as value for the id, for example

/summon Boat ~ ~ ~ {Passengers:[{id:"Cat"}]}

And my question is if in this case the OwnerUUID should be the UUID of the player using the command

@unknown and what if a command block activates it? or when a dispenser dispenses the Cat egg?

That would be a problem then. Leaving the OwnerUUID blank in this cases looks consistent. However this was rather a suggestion

Removed the spawn eggs for now.