why did the game review engine say that a pawn should’ve been promoted to a rook instead of a queen?

It doesn't say a rook promotion is better when I look at it. There's no reason for an underpromotion at all, either.
Sometimes you have to give it a moment; I once played a rook sac that was considered a mistake at first, but then it was brilliant when I checked again.
Edit: I looked at the wrong move. It actually says they're both equal (+M11), which makes sense, seeing as that piece has to be taken either way, meaning it doesn't really matter.