Me again! Your favorite software tester
See attached pictures. In the first (6 moves left) it says 11/15 instead of 15/15... there is no more dirt. Also, I did not get a goal achieved message. When I made another move it did say 15/15 and gave me a goal achieved message.
I'm theorizing, but if I had got to the end without any moves left it would have said no more moves and ended...incorrectly.