The issue here isn't code on the disc, it's the legality of this. You are licensed to use the disc only on the computer it is tied with if you've got an OEM license. The Intel Mac CD is licensed only for use on that Intel Mac.
As for why the code is on that disc, I'm thinking it may just be a mistake. Perhaps Apple didn't change everything on this particular disc when they updated it for a newer model. It's sort of like how 6.0.8 can boot a PowerBook 100, I guess.