Yes, it’s valid.
“I absolve you” is the essential form for Absolution…
The Priest must have been in a pretty big rush if that’s what he did.
Irregular, yes.
Invalid, no.
@FrDavid96 would this be considered valid but illicit? Or both valid and licit but just irregular and maybe a bit imprudent?
Don’t use the word 'irregular" as that has its own meaning in canon law, not related to this topic. Still, irregular in the typical sense of the word, yes.
It would be “illicit” in the sense of not following the prescribed ritual which the law requires, but not an “illicit sacrament”
A priest should not be doing this. However, I don’t know the exact circumstances. If there’s some good reason for doing it, it’s still valid.
Is a large number of penitents good reason? Typically no.
If the large number was unusual and the priest was caught off-guard? Maybe he typically has 10 people but he looked out and saw 40 so he knew he had to be quick? I’m just speculating.
I would rather see a priest do it this way (quick) because at least there is individual confession and individual absolution, than to see one who (possibly wrongly) uses the general (ie group) absolution without individual confession.
The important point is that what the OP described is a
valid absolution.
I’ll be the first to insist on following the rite itself as much as possible. I do not know why this priest seemed to be in such a hurry. Let us just hope he had a good reason.
The OP did say he was trying to hear as many confessions as possible before Noon Mass. Advent is typically a time when more people go to confession, and the priest might very well be surprised by the number.