The citation in the OP, "para f of FMCSA" is completely worthless, it tells you nothing about where to find the referenced text. The quoted text is found at 23 CFR 658.17(f). It's not part of the FMCSA, but the Federal Highway Administration act.
I find nothing which limits the quoted part to only commercial vehicles. Some sections, like the definitions and length sections, specifically reference "commercial motor vehicles," but not the quoted section, which references simply "vehicles."
But, it really doesn't matter, because the OP's interpretation is wrong. The section prevents states from imposing unreasonable roadway axle weight limits (I think most have seen axle weight limit signs, common on bridges) on Interstate highways in general. It's not there to force states to allow you to tow an RV with 20000 lbs on an axle/tire combo rated for 3500.
Referring to the enabling legislation makes that clear - it penalizes any "State [which] does not permit the use of [Interstate Highways] within its boundaries by vehicles with a weight of twenty thousand pounds carried on any one axle...". It's there to insure consistency within the Interstate system.
You can disagree. Come back after you successfully fight an overweight ticket in federal court.
