I consider my Nomad Mk II to be my heavy touring bike, my Sherpa to be my medium touring bike, and my titanium bike to be my light touring bike.
The Nomad Mk II was rated for about 60kg of luggage weight for my frame size, the Sherpa was rated at about 30 or 35kg. So, the Nomad Mk II was rated for almost double the luggage weight as the Sherpa.
When I took my Nomad Mk II on this road (first and second photos), I was really glad to have that bike instead of my others, I am quite certain that with my luggage weight that day, that I exceeded the weight rating for a Sherpa, but not the Nomad Mk II.
I have looked at the Nomad Mk III weight ratings (months ago), they were rated differently than the Nomad Mk II or Sherpa, so I was not sure if the Mk III is lighter duty than the Mk II Nomad or not.
On the topic of putting a 140kg rider on a super lightweight bike that a 70kg racer would ride, that makes no sense to me. If you want to put double the weight on the bike, you should expect the bike to need to be twice as strong with twice the materials, thus roughly twice the bike weight. And they should have wider tires to reduce the chance of a pinch flat. And their rims will need to be strong enough to handle the extra air pressure in the tires. Even their freehub pawls would need to be stronger.
The Co-Motion Americano touring bike made in USA is the only solo touring bike I am aware of that uses tandem wheels with 145mm rear dropout spacing to provide a non-dished rear wheel. That is not a performance bike, but if I weighed 140 kg, I would probably buy that bike because that bike is built for a heavier load.
A decade ago I fitted a suspension fork to my Nomad Mk II and rode the White Rim Trail in Canyonlands. A tour group operator provided the vehicle support to carry our gear, food, water, etc. for four days of camping. The truck in the third photo was a Ford F350 Superduty truck for that purpose, fourth photo is an example of the road. If they took a light duty pickup truck with an average weight rating on that road, they would have needed a really heavy duty tow truck to retrieve it.
Of the 10 bike riders on that White Rim trip, I was the only one that did not have a full suspension mountain bike. I had owned my Nomad Mk II for only a year and wanted to see how it handled a rough road. So I bought a suspension fork for it and I have to say I was quite happy with how the bike worked. When I bought the Nomad Mk II frame, I did not anticipate ever wanting a suspension fork, so when this trip became a possibility, I was quite glad to have a frame that could handle a 100mm suspension fork without upsetting the geometry.