10-bit vs. 12-bit HDR deliverables

I’m looking for help understanding where 12-bit color would be used for a deliverable format instead of 10-bit.

Both seem to support REC 2100 / HDR and WCG, and that 12-bit is technically better, but I’m curious if anyone has examples where 12-bit makes a noticeable difference over 10-bit?

It also looks there are no true 12-bit monitors in existence, so also curious how monitoring would be possible?