Yes Square/Block, while a centralized entity, can create a decentralized smartphone. Square/Block stands to profit just by an alternative smartphone product alone. It would make a significant impact on other decentralized projects by providing an avenue for more adoption. In fact, accelerating "mass" adoption. But I'll let @jack Blockhead answer whether they can offer a truly decentralized smartphone. If I was in Jack's position, I would definitely do it. Square/Block stands to lose nothing. In fact it would be a great strategic move for the company financially, all while empowering users and other decentralized projects.