I'd tend to agree with that. I know I started to notice my Vapor Trail's presence at about 28 pounds; at 32 pounds it was distinctly uncomfortable. (I know the VT has a fairly stiff framesheet; I don't believe there's a metal stay in there, but I won't swear to it.) I don't know what they do to beef up the suspension in the Nimbus Ozone.
I ended up switching away from my Vapor Trail to my Aether 60 simply because I was finding, too often, that I needed to carry more food for longer trips and/or carry 3 or 4 quarts of water. This ran my otherwise lightweight load up toward 30 pounds pretty quickly, and the VT wasn't doing the job anymore.

I've tried a couple of those pad-as-frame packs, and the only one that seemed to work well was the Six Moon Designs Moonlite (Starlite?) - and it had stays. It was about 5 years ago, and I sent it back because the torso wouldn't adjust long enough for me. At 35 pounds, it still wasn't as comfortable as frames with full, dedicated suspensions - but that could have been the fit, not the design.