I was analyzing a game on chess.com and it showed me that, in the below scenario, it is better to promote to a rook instead of promoting to a queen. It also shows that it has a mate in 6 with the queen, but it also a mate in 4.
I am not sure why chess.com thinks it is mate in 6 and why the rook move is better. I am only ~1200 so I could be missing something obvious. Do you have any ideas?
The game can be seen below, or here on chess.com.
[fen "2k3r1/ppp4P/3rp1Q1/8/3P4/4q3/PPP5/1K1R2R1 w - - 0 1"] 1. d4 d5 Bf4 Nc6 Nf3 Bf5 e3 Nf6 Bd3 Bg6 Nc3 e6 Ne5 Be7 h4 Nxe5 Bxe5 Qd7 g4 Bxd3 Qxd3 O-O-O g5 Ne4 Nxe4 dxe4 Qxe4 Bd6 Bxg7 Rhg8 Bf6 Be7 Bxe7 Qxe7 O-O-O Qd6 Qxh7 Qa6 Kb1 Qd6 Qxf7 Rgf8 Qh5 Rxf2 g6 Rff8 g7 Rg8 Rhg1 Rd7 Qh8 Rdd8 Qh7 Qd5 h5 Qf3 h6 Qxe3 Qg6 Rd6 h7 Rgd8 g8=Q Rxg8 hxg8=Q+ Rd8 Qxd8+ Kxd8 Qh7 Qc1+ Rxc1 c5 Rg8#