That tactis trainer puzzle is flawed to be honest. The king should have been moved to g8 once the queen's attack was removed. That would change the game and even opens up the possibility for stalemate, possibly checkmate, if black plays properly.

Never claimed that TT puzzle was difficult Gimpalersan, just less easy than today's daily one!

As for your assertion that it's 'flawed', you might want to go & look again because at no time can the king escape - remember that the white bishop is on g6 by the third move & cuts off any retreat via f7.  And anyway, what exactly does "once the queen's attack was removed" mean ?

Of course if you'd like to post your alternative line....?