It sounds similar to that antithesis testing service that was on front page recently as well. That also claimed to be able to run programs deterministically as well. I wonder if the two projects are related at all.
The most interesting part of Antithesis (to me) isn’t even the perfect reproducibility, but the autonomous state space exploration that finds the bugs in the first place. AFAIK Hermit doesn’t do that, though you might be able to get somewhere by running your program plus a conventional fuzzer under Hermit together?
Disclosure: I am one of the co-founders of Antithesis.