Why does this puzzle offer f8=R as better than f8=Q? Here's a chess puzzle that gave a confusing response.
https://chesspuzzle.net/Puzzle/52112
[FEN &quot;5R2/1p6/p4Ppk/3r4/7p/1P6/P7/1K6 w - - 0 1&quot;]

1. Rh8+ Kg5 2. f7 Rf5 3. f8=R

If you play f8=Q in this final position, you will not fail the puzzle, but be told &quot;There is a better move...&quot; (f8=R).
It seems inevitable that the black captures the promoted piece, and the result is the same after white recaptures.
Incidentally, f8=Q was played in the game. https://www.chess.com/games/view/15563079
What is more curious, is that I have played other puzzles on this site that allow multiple moves in a position for continuation, and my assumption therefore was that it only suggests a &quot;better move&quot; when your move doesn't change the theoretical outcome of the game, but gives significantly lower advantage (i.e. still decisively winning, but slower).  This would suggest that chesspuzzle.net has evaluated f8=Q to be an inaccuracy of some sort.
Is there any reasoning to be found for this?  Or is it just a strange computer evaluation?
I have tried inputting the position on the analysis board on lichess.org, and it flip flops between the two moves as the depth builds, but eventually starts showing f8=Q with a consistent advantage. (The opposite of chesspuzzle.net)
This seems strange also, as in my perhaps naïve reasoning explained initially, both moves should be identical.
If anything, promoting to a queen is the better choice, as it forces Black to exchange their rook. For promoting to a rook, Stockfish NNUE actually slightly prefers moving the f5-rook away instead of playing ...Rxf8 (although any continuation gives White a large winning advantage). So at the very least Black is given a choice.
But even if we were certain it's best for Black to play ...Rxf8 if White promotes to a rook, there would still be no reason to say that promoting to a rook is better than promoting to a queen - both lead to the same outcome. What possibly happened is that the site's computer calculated one line further/differently, and arrived at an evaluation that was higher in the line for promoting to a rook. Although since you said the site allows multiple solutions to sometimes be accepted, this seems like a bug in their software.