Bats still move with slowness effect 7

I am trying to make it possible for players to set a teleport spot for later use when using an item. So now I was trying out different things to spawn on their location that can have custom names, can be made invisible, invincible (resistance effect 5 maybe) and have no player collision, so they can not be pushed away from this location. I came to the conclusion that maybe a bat would be the best for this, but it seems bats are not effected because they are flying.

So yeah. Maybe this is on purpose or a bug, but it still would be nice to have a mob that meets this criteria.