Earlier quoted context omitted.
He's not saying that Apple has a monopoly on smartphones; he's saying it has a monopoly on iOS. His overall point is that while iOS has a strong lock-in effect for people already on the platform, in China the real platform is WeChat, so the iOS monopoly isn't as useful.
No, he is saying that Apple has a smartphone monopoly in the quoted paragraph.
> Moreover, the advantages go beyond margins: the best way to understand both Apple’s profits and many of its choices is to understand that the company has a monopoly on not just MacOS but even more importantly iOS. That means Apple can not only capture consumer surplus on hardware, but developer surplus when it comes to app sales; that some apps are not made is deadweight loss that Apple has chosen to bear to ensure total control.