HomeschoolDad:
Do you mean that priests do this, even when they simply attend Mass? I don’t doubt that they could , if they wanted to, but can’t they just sit in the pew and assist at the Mass, the same way a layperson would?
Yes, in some circumstances priests will just sit in the pews and “attend Mass” like a layperson would. The most recent story I heard about that involved one of our local priests who took a vacation down south (before all the COVID hit) and attended a local Sunday Mass there in his lay clothes and the other parishioners were so happy to see a young man attending Mass (since apparently that was a rarity at their church), the priest didn’t have the heart to tell them he was actually a priest on vacation. Obviously he wasn’t exercising his priestly office from the pew in that case.
However, I think there’s some guideline or rule that came up when we last had this discussion that said priests should usually be acting as priests when they are at Mass.