i can offer no concrete evidence, but the impression i get from within the gamedev community is that this is generally accepted to be the case.
there are ample hints that this is fits with Apple's philosophy for the app store. the fact that they forbid you from mentioning if you are on other platforms being the most easily verified.
if you are ever lucky enough to meet with some of the Apple guys to discuss how to help your app on the store then you might be able to find out for yourself whether this is bullshit or not.