This. In fact this is quite common in Chinese domestic market phones too. E.g. The Vivo branded (subsidiary of BBK who is also the parent of Oppo and Oneplus)

This. In fact this is quite common in Chinese domestic market phones too. E.g. The Vivo branded (subsidiary of BBK who is also the parent of Oppo and Oneplus) phones are generally domestic market targeted and use FuntouchOS which has arguably adware/spyware built in to the OS level. It's also impossible to flash a custom ROM as it has a locked bootloader.