I agree with you. The failure of the primer and web is a loading issue, not a headspace issue. Pardon me for the observation, but Englishmen seem to find sudden headspace change/failure at every juncture of firearm dilemma. Headspace does not generally change between shots, and can remain constant for a century if not stressed by overloading. I have several rifles that fail a SAAMI sporting "no-go" gage but pass on a Service Field Gage and are therefore safe to shoot. I agree again, wrong test standard. In short, that was an ammunition problem, plain and simple.
As to the two tales issued, well heck, I'd have been polite, then irate, then I'd have held their feet to the fire in every web forum and pulp media I could find. (Screw 'em!)
But then, I'm an uncouth Yankee.~Muir