is "Useful proof of work" real or just better marketing?

I have been researching different projects recently and I keep seeing projects say their mining does AI training or protein folding or whatever instead of just securing the network.

is there actually a technical difference or is this just regular mining with a better story? like at what point does the "useful work" become genuinely useful vs just something they tell VCs who want to invest.

I'm interested if anyone's looked into this further than I have? Can anyone tell me about any information that you have found?