I've not actually touched a Rousseau/tekton but I assume it's really no different than a lista or vidmar. The slide mechanism doesn't affect what happens to the drawer itself if you put a lot of weight in the middle.
Fwiw, I like the slide mechanism of these better than the more common cartridges used.
Yeah, it's pretty much identical to Vidmar.
The drawer design is different on the heavier boxes, partly due to the way the slides are incorporated. It's almost a "post hoc, ergo propter hoc" scenario. The drawers are heavy duty, therefore they have a heavy duty slide mechanism. But part of the reason they have that slide mechanism is because the weight rating of the drawer needs it.
You should be able to put the full load rating anywhere in the drawer and still open it and close it.
I know I put lathe chucks and extremely heavy tooling in the center of my Vidmar cabinet drawers and they don't behave any differently than a drawer loaded evenly. A 12" steel lathe chuck weighs over 150# pretty easily.
A wider drawer might encourage a person to overload a drawer perhaps.
That's a lot of words to say I basically agree with you.