That's not true in the production world anymore. Updated European safety standards in the early 1990s caused manufacturers to move to oversize tubes on their steel bikes and equivalents in fatigue resistance and overall strength in their aluminum and carbon bikes. Used to be a road/touring bike had 25.4/28.6 TT/DT but now it's all 28.6/31/8 TT/DT and it shows in the weight and ride quality.

For light touring under <20 pounds full load I would never consider a production touring bike. They're overbuilt for that purpose and would ride poorly for an average riders weight with that size load. I'd much prefer an endurance road bike, regular road bike with rack mounts or even a QR mounted front rack. I finished an overnight last week on an endurance road bike (soma fog cutter) with an 11.5 pound load mounted on a front QR rack, it was a very enjoyable ride and much better than when I had a touring bike and tried similar.