White could have won the Queen with 10 Rxa7, but White is 620 centipawn material up, so that 10 dxe5 wins just as well. So 10 dxe5 is a "blunder" in the sense of 570 centipawn loss, but not a "mistake" in the sense of changing the outcome of the game: White wins anyway. I agree with the way it is handled. It makes sense.
#4 Probably it's like tpr says. White will win anyway. Handling it in another way might lead to silly situations I guess if there are many moves that obviously will win but only the "best" is considered correct.