all depends on what actual compound the michelins and bridgies are...
i'd imagine the hard and medium compounds are only relative to what each company brought to the race meet... ive no doubt that the "hard" tyre from catalunya to malaysia will be different compounds and you may find that the "medium" at one meet is more like the "hard" compound at another track...
that and how riders work the front and rear might be different, maybe casey doesnt push the front as much therefore doesnt heat it up as much... who knows....
but then again ive only been riding for 20 months
tho i have been watching racing for much longer... i am old enough to remember watching the 1990 phillip island GP... and watching it many times on tape... gotta love the 500s