I’m not sure that’s true. If that were the case, then we wouldn’t have many people on this thread and on BYC in general reporting that their broodies removed and/or ate the unfertilised eggs in the nest.I don’t think so. If they realise their eggs are infertile, the hens would not try to hatch them.
Females, hens in particular, are very aware of what’s going on with their eggs. My (rather unscientific) conclusion is that they do know that their eggs are infertile (since they’re also aware that they’ve never mated with a male), but choose to ignore it because their hormones are calling them to express this behaviour