We've always required a game registration on your account before you could get to standalone patch downloads for GC2/Sins, as far as I can remember. I believe GC1 did as well. But the third party sites have typically mirrored the files anyway, without authorization. I believe Brad has commented that this is one of the reasons we've had to go with SDC/Impulse.
See, our support and often huge updates for legitimate users are how we get people to make the honest choice, since we don't use any protection on retail copies. If any site can mirror the patches for anyone to get, then that basically shoots the whole idea because pirates can just grab them like everyone else.
With SDC/Impulse though, legit users can get easy and immediate access, and pirates are left out in the cold.