Even China doesn't rely on controlling information from the user-side, they know any devices can be hacked lol. They rely more on controlling the server-side (WeChat, Douyin, Weibo, Bilibili, etc) and infrastructure (GFW).

Well mostly, aside from some exceptions like (allegedly) Apple's AirDrop limitations.

Many Chinese brands still support unlockable bootloader: https://github.com/melontini/bootloader-unlock-wall-of-shame...

Although going forward, there's a strong incentive for manufacturers to follow Google and lock their devices.