Brad.. re the composing of a list of "R" tyres based on treadwear numbers.. see the below from wikipedia
'In general, manufacturers tend to overstate the treadwear of their tires in an effort to create the impression that their tires last a long time. The exception to this is in competition racing tires, which customers expect to have very soft rubber compounds and very short lifespans. Manufacturers tend to give their race tires low treadwear numbers (often zero) to emphasize how soft and sticky their rubber is.'
Unfortunately treadwear numbers are at the mercy of tyre manufacture marketing departments, they can't really be used for the purpose proposed.
jim ~
well this makes it quite easy then to discern R tyres. Your supporting quote actually supports opposing argument to yours. If manufacturers are over-emphasizing the stickiness of a tyre by a low treadwear and durability by a high treadwear factor, no tyre is to be found at 100 which should then be used as a cutoff!