I wonder if the exact temperatures involved are the key. If most of the good volatiles don't leave the hops until ~140 or 150 F, then as long as they have careful controls, they can get away with heating at 135 F for a short time. However, at home I know my oven doesn't even let me set it below like 170-175 F, which would not be a good thing if I lose a lot more volatiles at that temperature. And I think for many ovens, the temperature would be very unstable at low temps, so you'd need an oven designed for low temps.
Long story short: maybe dehydrators are best for homebrewers. Otherwise... Don't try this at home.