It is correct, but I'd add that the adversarial environment means that if 51% of miners were to collude to take some portion of the money, they'd rather collude

It is correct, but I'd add that the adversarial environment means that if 51% of miners were to collude to take some portion of the money, they'd rather collude to take all the money, which takes away the incentive for anyone to arrange a fork to do this, and if that were going to happen it would be happening all the time. What would probably actually happen is that such a fork would be obviously illegitimate to users, exchanges, etc and people would use the unforked chain deliberately, and after some hash rate adjustment and delayed block times, the forked chain, even with 51% of the hash rate, would be close to valueless. Miners don't like mining valueless chuck e cheese tokens, so their hash power would return to the broadly accepted network. This BTW demonstrates a security property of PoW that you don't get with PoS: you can't mine two networks with the same hash power, you have to pick one or the other. If bitcoin were a PoS system, validators could just stake both chains and make a riskless bet on the winning one, and even benefit from both.