I am not a fat guy, and I don't do campfires.
I did stay at a Holiday Inn last night.:B
Sooo, with all of that I am extremely qualified to comment on this.
Lots of blanket statements being thrown around. Some have a tiny bit of truth at their core.
GVWR SHOULD be what the manufacturer rates the vehicle based on it's lowest rated part. That can be an axle, the frame, tranny, any part of the brake system, u joints, or countless other things.
The manufacturer never states just what the limitation is.
With enough research, one may be able to get a pretty good idea, but can never be 100% sure. Only the manufacturer knows for sure.
To complicate it further, some trucks are well known to have an derated figure such as 10K to fit in with zoning HOA, registration laws etc. Manufacturers sometimes do this for marketing/sales reasons. There is no harm in this, BUT.....
This is what gives some who want to ignore the rating their justification for using things such as axle ratings, tire ratings etc. as their "personal" limit.
This method may or may NOT be OK. If one decides to ignore the GVWR, and use an alternative method for their limit, it is up to them to accurately assess the capability of the vehicle.
Some may do a pretty good job of this (likely those that are fat and sit around campfires:B)and most likely will not.
From my experience with people... Everyone thinks they are an expert. Very few really are.
Where this gets irresponsible is when people that MAY be an expert at this make blanket statements that may be true for their particular vehicle, but not for others that may read what they wrote and mistakenly think it applies to the vehicle they own.