If you didn't like that example, the fact is that White cannot necessarily force mate in KRK even from White to play positions (which rules out stalemates and hanging rooks); in fact from the majority of White to play positions.
Here is another you might like to try. See if you can force mate from the final position (shown) against the computer.
Sure. The final position occurs on move 2, when white correctly plays Rh1#.
It does prove that, when faced with a chess position which is obviously, clearly and definitely lost for one side, btickler can't tell it's lost. Fair enough, because he's a weak player but next, he tells others that they can't tell it's definitely lost either.
So if Carlsen, Fischer, Kasparov and Capablanca were lined up and agreeing that it's won for black, he'd be telling them that they can't know that. I wonder who has to give him permission, before he can agree that it's won.
Yes, Carlsen, Fischer, Kasparov, and Capablanca would all be wrong. Quite obviously, as well.
I suppose you're the kind of person that believed the 4 minute mile would never be broken...you know, because the runners said so and who knows more about the human body and it's capabilities to run than a runner? Lol.