This is how BOINC and similar distributed computing projects work: a unit of work is distributed to multiple workers to confirm the work and discourage malicious actors.
The other very important part of BOINC and the like is that they offer no monetary gains for your contribution. That's how you eliminate 99,9% of malicious actors and the rest can be eliminated the way you described
It won't work in the PoW scheme because there is presumably some cryptocurrency involved as a reward
It won't work in the PoW scheme because there is presumably some cryptocurrency involved as a reward