snd_hda(4) clears all pin widgets at attach, don't do that if the user requests it.
Works for me as-is in 13.0-CURRENT @r339912M & 12.0-BETA2 @r339910M. 11.2-STABLE @r339881M needed the original .Dd line in the man page patch tweaked a bit to match expectations, but the text of that change and the code changes work as-is.
Have you tried to investigate whether keeping only VREF_ENABLE_MASK would be enough? It could have some more sense in general, since the driver has no way to know what VREF is needed in specific case. Same time other bits there are pretty logical.