For starters, I'm not convinced it would be harder to spoof that than the library information (which also seems pretty easy to spoof if not easier).
But even if that were the case, why would they spend this level of engineering effort just to be able to fingerprint people in that extremely rare case of having a spoofed phone model? Do you think that kind of customer would even be receptive to targeted ads in the first place? It just doesn't make sense to me.
