Ah yes, that is the key, thanks for saying that because I suspected that but wasn't sure if that's how I should think about it. So in the Rubix cube example, some people might get a cube that only takes a few turns to solve and others that may take thousands of turns to solve. But someone is going to get done first to claim to be the winner and then "new Rubix cubes" for all and everyone starts new again building off of the last winner.
The key is, everyone is creating their own puzzle to solve, it's not like there is a central server handing out puzzles. I think that helps with the confidence of people that it is not just a server in the sky giving out equations to solve (where one could argue it could be tampered with), but the client itself creates the puzzle. So being untruthful to yourself (hacking the client for example to report fake blocks solved) means nothing because you won't be able to prove it to others and the others won't acknowledge you, so you don't get credit. Very ingenious.