I agree, and also there's something communicated by the brand iPhone that is important. "Apple phone" communicates that this is merely Apple's version of a thi

I agree, and also there's something communicated by the brand iPhone that is important. "Apple phone" communicates that this is merely Apple's version of a thing, the phone, that many manufacturers produce. "iPhone" is a noun, its own distinct category of thing, that you can only buy from Apple.