It sounds like you may well be close to the truth there Icenian. The logic behind what you were told by the Dunlop man makes sense, although it would be very difficult to prove that the tyre was unstable; if other components were worn (even though they were still withing normal working limits) it would be a lot easier to show they were to blame rather than a combination of those factors and the tyres. Most likely rider error would be the one. In any case, it doesn't quite explain why, for instance, an XTZ750 or a Elephant 900 i.e. of the same age as an XRV750 can wear MT60s, but the XRV cannot.
I do suspect a degree of 'newism' here - that phenomenon where a punter is more likely to part with his or her cash if the product is ostensibly 'new'. Most of the time it's a styling job. After all, there is a limit to how 'good' a product (be it a vehicle or a consumable like a tyre). Not that I'm saying it might not one day be possible to make a tyre that is cheap, lasts long and has fantastic grip in all conditions and on all surfaces, but it certainly isn't in the interest of the manufacturer to make one like that! As a palaeontologist I notice that the common conception of evolution is some kind of progression toward some kind of top species (traditionally regarded to be Homo sapiens sapiens of course!). But this is a load of tosh - evolution works only within the frame of what works best for the problems at hand. Specialists normally are the ones that get hit during extinction events because they don't have the capacity to adapt. That same misconception about evolution applies to a certain degree to products like bikes and tyres. Someone here said recently that we have to accept that our tyres are a compromise, and the same goes for a bike like the AT. That's what makes it such a great bike - it can do it all. A bike that can take on all roads has the capacity to carry on when sport bikes that need flat smooth race tracks to work (or keep their alloy frames intact) has to call it a day.
That begs the question, why did the Africa Twin become extinct when the GSXRRR survived....?