This is only required if you want to use Liveupdate from within CCS (which works now!). The LU system will need to verify the files d/l'd from LU and that's why it's needed.
If your policy says no internet, then no problem. CCS will install fine. The only functionality you lose (I believe) is LU.
(I've installed CCS 11 in labs and in production environs without internet access)