I think the current behaviour allows a different kind of cheating, no? If I reach a point on a board where there are multiple possible solutions, then I could refresh the page to get a new board which (maybe) doesn't have the same problem.
Anyway, now that you mention it, I think it WAS the World 3 Boss; having finally beaten it a second time, I might actually have gotten the victory screen, but it looks so similar to the Game Over screen that I didn't realise it 😅