It is a move taken in lockstep with EU's Chat Control and UK's Online Safety Act, and the proposed Kids Online Safety Act in the US. The common objective of all is total control of digital lives of citizens and allowing the government to snoop on all internet communication while not disabling end to end encryption. They need end to end encryption to lock out external adversaries (Russia China etc) but they need to see the contents of encrypted messages to monitor internal adversaries.
First step is blocking you from running any apps not allowed by Google/Apple.
Second step is putting in the systems to snoop on end to end encrypted communication apps on the endpoints, enabling intel agencies to detect thoughtcrime without exposing everyone's chats to Chinese/Russian intelligence. This will most likely be done by OSes recognizing the apps and extracting private keys on demand.
Last step is locking the bootloaders so you cannot have a phone which lacks the 'features' added in the second step.