Here is an article from OWC, a trusted vendor:
In short if you want an internal SSD or larger HD you need to purchase the ones Apple provides when ordering.
If you have additional feedback please channel that to Apple at www.apple.com/feedback. Not that you are commenting about the following but just to nip this discussion in the bud these forums are to discuss technical issues only. Discussion of Apple's policies and decisions is against the Terms & Conditions of this forum.