Many consumer devices can be selectively targeted for updates. The entities that control the update servers are controlled by the states that they are a part of. People seem to have forgotten that companies once felt the need to invent warrant canaries to warn when they had received non-public court orders. Presumably they can also be forced not to remove the warrant canary.

Edit: My first read had me interpret backdoor as any undetected means of gaining access to a device/system. I have updated by definition to mean using a flaw in the system left intentionally to gain access. This somewhat negates the need for my previous comment, but I'll leave this for illustrative purposes.