The paper (fiber) base softens, making the wet print more susceptible to damage.
Yes, soaking paper in water makes it disintegrate when you leave it long enough. There's a difference between a fairly rough flow of water in a tray with a siphon and a vertical print washer, though. The print washer is very gentle in its agitation and the flow-through isn't as rapid as in a tray. A hour in a print washer won't hurt the print, unless you're printing on paper towels.
Anyway, I let it go for about 40 minutes. I mentioned an hour in reference to the fact that it was spouting water onto my floor.