The gray horizon has been leached of iron and humic acids, which have been deposited in the middle of the profile
Neat, a lot of the mushroom books just say podzol but I believe they also grow in some "sandy soil habitats" as the mycologists say so would that be an example of a spot where it's not actually podzol as you're saying?
The books also say we have podzol "everywhere" in the Pacific Northwest from the volcanic activity but I expect that to be a generalization.