The bug

Tripwire hooks with the "attached" state set to false and the "powered" state set to true are impossible to encounter in normal gameplay, since in order to be powered, tripwire hooks must necessarily be part of a tripwire circuit, and therefore attached. I've done in-depth testing to confirm that this is the case and that this block state combination cannot be encountered.

However, despite this, this unencounterable block state combination still has its own explicitly-defined model file "tripwire_hook_on.json", even though will never be seen in normal gameplay.

The only differences between this model and the attached on model is the lack of a tripwire element, as well as the fact that the ring is positioned differently, potentially as a fix for MC-69834 or some other issue that never got applied to the unattached powered tripwire hook since, again, it can't ever be encountered normally.

Note that this issue differs from some other unobtainable state combinations such as those of walls or redstone wire; those arise due to how the "multipart" specification works, whereas this tripwire case explicitly defines a model which can never be seen.

How to fix

I've attached an updated tripwire_hook.json blockstates file that points this state combination to the normal unpowered unattached tripwire hook model, so this can replace the existing tripwire_hook.json in the blockstates directory. The model file "tripwire_hook_on" can be deleted from the models/block directory as it will no longer be used at all by anything.