We have ‘muscle memory’ in our visual cortex as well. So, we can train ourselves to spot stuff that is normally pretty difficult to spot with practice.
The morels being brown, and fruiting in leaves from last fall, it makes them pretty difficult to see.
Aside from that, they probably have a good idea of what spots to hit because they’ve been hitting those spots for years. As well as a understanding of good conditions to look for them, without having the knowledge of those conditions that I just gave.
And… Mushroom foragers are usually pretty sketchy about giving up their good spots.