I have an opinion, but I haven't toured extensively with waterproof packs so it's not very informed. But I agree with the language about condensation because it makes sense to me based on my experience with packing things in plastic. I travel with two panniers. One holds my clothing, insulation, and maps and paperwork, which I protect carefully with a large trash compactor bag. Nothing wet ever goes in there. The other holds shelter, tools, and food (separately packed in plastic) which I let get wet. I like having that flexibility when packing up on the wet mornings. The wet stuff eventually dries out without too much fuss.

The argument sounds a little like the waterproof footwear one in the hiking world. Do you try to keep your feet dry, or just wear well-ventilated shoes, let them get wet, then they'll dry faster? There are experienced hikers firmly in both camps.