ha ha first haha
Practical Puzzle
The goal of the problem shouldn't be white to play and queen in 6. Rather white to play and win. Because even though you say "of course not 2...Kxd6", that isn't really worse than letting you queen. Yes, black loses both ways, but I think it might even actually take longer to mate if he gives the rook.

Isn't 3. Kc6 just as good?
You are correct. However, as it is only possible to display one solution, most people go for Ke6 first so I put down that one.
This arose in a game of mine. White to play and have a queen in 6 moves. Do you see it?