> I would think they want to decouple from ARM and the west in general as a dependency.

Why would you think that? ARM is not like x86 CPUs where you get the completed devices as a black box. Chinese silicon customers have access to the full design. I guess it's not completely impossible to hide backdoors at that level but it'd be extremely hard and would be a huge reputational risk if they were found.

They also can't really be locked out of ARM since if push comes to shove, Chinese silicon makers would just keep making chips without a license.

I did catch one vendor using a HAL across a whole SoC product line, a very low-level HAL that sat between SoC hardware registers and kernel drivers. It effectively made the drivers use scrambled register locations on the AHB etc, but if you resolved what the HAL did, the registers matched ARM's UART etc IP. So I figured they were ducking license fees for ARM peripherals.