Why would number of lenses imply number of photos taken? The idea that Air users will take fewer photos than iPhone 17 users because they have fewer lenses doesn't strike me as an obvious conclusion. Photos taken by that single lens take up the same amount of storage space as photos taken by the two-lens iPhone 17.
I suspect most people's storage use is cumulative over many years of using an iPhone. Most people don't buy a new phone and proceed to fill it up from 0% to 100% via photos taken on that device. Most users bring XGB of data accumulated over the years, and then use an additional YGB of data by accumulating new data during the ownership period. So I bet a majority of users' storage use is preordained at purchase, only to marginally increase over the ownership period.