I think it's the same as warnings against high humidity, 75%+, where the real concern is dramatic spikes in temperature and humidity with a lack of air flow. I don't grow DWC so I figure my opinion matters little but if one used
@derek420colorado max O2 method in a light sealed reservoir there wouldn't be any problems but I'm just speculating.
I'd be interested to hear
@Mañ'O'Green take on it though