Unused block model file

Maybe it's being implemented in preparation for future updates?

is this not the chorus plant with all connections possible? in that case it's not unused as commands can place it.

No, that is not the case. Chorus plants are not ment to work like that. Check the blockstate file.

Hm, you're right, the block state file indeed does not reference it at all.

This isn't a bug and the model is used. It's the inventory model for chorus plants and is referenced from assets/minecraft/models/item/chorus_plant.json