Were Google just one of many available app stores for Android, would this be a weaker case? (Or: would railways have been regulated as common carriers were there several parallel railways next to each other, or if the track owner was not the only person operating trains on the line?)

What if OS + Store integration was done at the cell phone manufacturer level? What if they all ended up settling on the same default store (say, Google's?)? Would it depend on why they had selected that one? Would it depend on how many others existed? (And same question if OS + Store integration was done at cell network operator/phone reseller level.)

What if there was a plethora of app stores that various phones came with, but they all or almost all independently decided an app was not representative of them, or distasteful, or inappropriate?