I generally hold a similar opinion. However I have two data points that suggests back-doors are not available by default (for my government at least), but that they are aggressively bugging (or auditing, lol) devices:

* When I ordered the first generation Raspberry Pi, they were stuck in the toll a long time, and when they arrived all the warranty seals were broken. Consequently I never really used them.

* When I ordered the first generation Google Pixel, before it was generally available in my country, it was stuck in domestic mail for almost a week. The person who imported them sold and sent two phones the same day: the other one arrived after just two days and travelled a lot further. I used it regardless as I already considered phones a lost cause... (and could not with good conscience sell a possibly compromised device).

At this point I don't trust anything sent by mail.