Hmm, I'm tempted to say yes, it's better. Instead of getting blocked from the game entirely if the internet is absent, you can play it well into the campaign. Assuming the progression design is similar to the current game, that means a hefty length of gameplay before reaching a point where the extra content becomes necessary. Somewhere in that interval, hopefully everyone can find a way online.
I think they should make a Disc 2 available as well. As he said, in the current Forza, Disc 2 is the same as DLC. It needs to be installed to the HDD to be usable. They could treat the added content in FM5 the same way, for people with no way online.