I wasn't so much as questioning the timed exclusive as the reasoning behind beta testing a platform that wasn't the breeding ground for the bugs to begin with. Rather than assuming I am a fool and answering my own questions, perhaps a little deductive reasoning? It seems counter-intuitive.
It's not like the Beta was born
because of the PS3, your singular platform isn't that important so as to create the need for the Beta by itself.
It's for many reasons that the Beta is being handled in this manner.
One is the timed exclusive. If they were to allow PS3 users into the public Beta, then it would most likely violate the terms of the timed exclusivity agreement where 360 users get access to the DLC a
full thirty days before anyone else. Like others have said, blame Sony for not competing for the exclusivity, not Microsoft for money well spent. It's Sony's fault that you're not getting the DLC first.
Reason two would be because there are no bugs that the PS3 is having that the other platforms haven't also had. Since the same bugs seem to stretch across all platforms, it's simply easier to use the platform you designed the game on to Beta-test the bugs/glitches out of it.
Third reason could be common sense. Why would I have any kind of test on the system that runs it the worst? Then you wouldn't know what's a bug/glitch apart from just that particular console having a crappy port to it.
PS3 users aren't getting shafted with the Beta, they're getting shafted by their own console manufacturer.