Actually
Actually, there is some truth, but its not Intel telling Apple not to use it.
Intel yanked ATI's license for using the Intel CPU bus for chipsets. Not just for graphics, but for chipsets. This means that ATI can continue making PCIe graphics, but not northbridge chipsets with integrated graphics for Intel processors.
So, for example, a Mac Pro could still use an ATI card as it would be an expansion card, however usually when embedding graphics you go for the most cost effective method, and that is: If you can get acceptable performance from a northbridge chipset graphics adapter, go with that.
If nVidia has the nForce and Intel has IMA graphics integrated, then they both have cost advantages in the mac mini market, as well as the iMac and MacBook markets. ATI will likely only exist as an option in full blown desktops unless you have AMD processors.
What does this mean for ATI? I think its bad news, just as they finally started shipping real chipsets, just like everyone else in graphics is now starting to do, they get their license yanked as laptops become the most popular type of computer....AND as Intel dethrones AMD on power efficient processors. Overall, bad, bad idea... AMD loses their whole laptop market because NVidia is making the nForce and because Intel is slowly improving their graphics capabilities.
So.....MacPro only, maybe xserve.