Well, this actually makes sense, because you can't use the app you download on the App Store on a Microsoft Surface. Maybe that's obvious to you and I, but the App Store is used by hundreds of millions of people of varying levels of technical knowledge...
The worrying position would be if Apple demanded special features for the iOS version of the app, or if they asked you to get rid of the Microsoft version altogether. If we got to a point where stories/rumors like that started to emerge, that's when everyone would be in trouble.
It's getting pretty absurd how people excuse Apple for these things. Of course an e-commerce app might show a product they sell on one of their screenshots...
You can certainly use the app you download on the App Store to purchase a Microsoft Surface. They object to any depiction whatsoever of any other platform.
The worrying position would be if Apple demanded special features for the iOS version of the app, or if they asked you to get rid of the Microsoft version altogether. If we got to a point where stories/rumors like that started to emerge, that's when everyone would be in trouble.