Okay so this has just occurred to me.

Terapagos should be OU.

It cannot actually gain its Uber-level stats without tera'ing.

These are separate forms. Like megas. Thus they should be tiered separately. Tera'ing, for Terapagos, is exactly akin to Mega Evolution.

Hell you could even make this argument for Hearthflame, although there are no stat changes, only ability and typing. Although ogerpon also has an item slot restriction just like a mega.

Terapagos and Ogerpon are the only pokemon who have special tera mechanics, right?

It would surely be incredibly easy to simply grey out the tera button on these two pokemon, and trial them in OU.

This isn't a complex ban, this is tiering separate forms separately, which is something they have always done. I can only imagine it's policy bureaucracy autism preventing this. Either that or they just haven't thought of this. Or they just don't want to shake up the metagame anymore.

Pros: OU gains a spinner
Cons: Another annoying 600 BST threat to worry about