apple doesn't have to make all their filetypes different to work with their system.
You're still missing the point. iTMS videos are MPEG4—not some Apple proprietary file type. The content creators
want DRM protection, and Apple can control only their own software and hardware. A given user can "authorize" a certain number of computers and other devices to play that content.
Apple is typically very open, using common file types that will work anywhere. This dates back to the company's beginnings. The AAC audio sold through iTMS (which, again, is no longer protected by FairPlay) is MPEG4 audio, a later generation of MP3, although some detractors will erroneously call it "Apple's audio format."
Apple's iWork suite of tools can read and write MS Office formats—which are proprietary to another company. (OpenOffice is another option.) Many apps on different platforms will read and write common file types even though each app may have its own proprietary "project" format. For example, Apple Final Cut, Adobe Premiere and After Effects, and Avid's editors all read and write a common set of video formats, even though they have proprietary project formats.
Apple got smart and made the iTunes app available on Windows as well as Mac. Similarly, Amazon made Kindle software available on numerous platforms because it was in their own interest—they're primarily a content seller, not a hardware manufacturer.
I routinely work with multiple platforms, and sometimes must convert document formats—but never because of platform
. Anyone who makes a claim such as the above quote is either misinformed, or has some ulterior agenda.