Reported on Godot forum by xyz user:

"When I placed the last tile in the deck it said "sorry no more moves" instead of congratulating me on a win. I might be wrong but it looks like the game first checks for losing and then for winning conditions. It should be the other way around."

Looks like it is a misunderstanding about the "empty deck" and the end, as when the deck is empty, there is still ONE tile in hand to play and if there is no move available for this very last tile, it's game over.