I know that Jim is right that not one rifle has ever blown up due to lug engagement (He didn't say that but I'm just assuming). I do think that most clearances are so small that initial "set-back" will take care of this.
Still, I feel that headspace close to the no-go limit and sizing cases like the manuals tell you to (bump the shell holder against the die bottom) is A cause of poor accuracy. For the cartridge to be laying in the chamber of a rifle with .004 or .005 clearance and the clearance dimensionally in diameter is a very good recipe for innacuracy.
Now, I know some will disagree, but when I fit a barrel to an action I want it to just barely close on a "go" guage, or maybe set so that the cases I use experience a slight "feel" upon closing the bolt. This way I know that the datum line in the case neck is in contact with the chamber and bolt face.
This way the bullet is hopefully better aligned with the rifling throat (paralel or otherwise - a different subject) and gets a good start in life!
This gentleman is very astute to do the check he did and just not accept the factorys word that "this is a NEW rifle"!
With me, headspace and lug engagement tells me lots about a manufacturer.
More years ago than I care to recall I wrote Mr. Willian Ruger a personal letter pointing out misalignment in barrel and cylinder alignment - He kindly replied with a personally signed letter (which I proudly have to this day) and told me he would give it to the engineering department for correction.
Also, the belted magnum case is the most dangerous case we have today. We are slowly getting rid of belts on cases and I say Amen!