After all, ads earn them revenue. You can have product differentiation where your devices don't have to necessarily earn by ads. A very good example of this is Amazon. They have two versions of Kindle, with the ad free version costing more.
GP is claiming that Apple is doing better in the phone space, because Z>X. But the appropriate comparison is not Z vs. X, but (Z+0) vs. (X+Y).
For high end devices, maybe some of the services could have been considered paid off for before and could have skipped ads. That way, even Google gets 'Z' from phones.
This just cuts into privacy as a marketing point for iPhone.
By giving it out almost-free to OEMs, Google solidified the majority marketshare as the cost leader. That is much more strategic than dumping capex into manufacturing against an already established quality brand.