Copper stub outs for PEX installation in existing home (SE MI)

I know plumbing codes can vary from state to state or even county to county, but, in general, are copper stub out elbows "required" when installing PEX in a exiting (50 year old) home ? The alternative of course is a 90 PEX fitting with PEX coming out of the wall and a valve crimped on to the PEX.

There are still a few places which do not allow PEX at all, but if they do there would be no reason to not allow a copper stubout. It is preferred by many as it is easier to properly secure in the wall.