I agree with the above- with the regional flights it happens with some frequency.
I flew during the US East Coast winter storm at the beginning of the month (IRROPS) and wasn't surprised that my onward A350 flight got swapped to a regional 772 whilst I was still inbound from the US. Stuff happens, aircraft type isn't guaranteed for any airline.
On the plus side, since the regional 772 doesn't have PEY, I got bumped to J in that case.
