Actually, I've HAD problems with the fuel drained back into the main fuel jug. I don't think it's the humidity as much as the waste resdue ie., oil from the aircraft tank. the % of oil is higher, there are unburnt hydocarbons, ect.
I was having a problem with a relatively new engine and of course had 1000 different suggestions from those at the field, one guy came up and offered his new fuel jug. Problem solved!!!! The engine worked beautifully.
Anyways, since I started using the small storage tank & burning off the old fuel on the firrst flight I've never had anymore engine "problems". And, I've been doing this for over 25 years. so experience wins over "thinking"
It is NOT overstated.