You mistakenly think that Microsoft wants a distinction between the two. They don't want you to rent a game or buy it used, they want you to buy it new.
I don't think Microsoft is pushing this, I think its coming from the publishers. They have been bitching about the used market for years. I guess they are not big fans of capitalism!
But to that point, you are correct - they don't really care if its rented or used, they want you to buy a copy of it since thats where they make money.
I don't see how this is Microsoft's problem to address in the console since its really a problem the publishers need to solve.
Besides, this is total crap anyway. It would be like OEMs preventing PCs from running pirated versions of Windows.
Or even better, like Apple preventing beige-box PC from running OS X.
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Tigger
Vic Fontaine for President