Think about this from the perspective of a Chinese government spy agency. If you are going to spend millions of yuan developing a secret spy chip, are you going to spend it on a phone model that only has 10k orders per year? Are you going to waste your resources on a phone that uses an NXP or Allwinner processor that no other phone model in the world uses, and has a BroadMobi or Quectel cellular modem that no other phone model uses (because it was designed for laptops)?
Frankly, I doubt that a Chinese spy agency is going to target phone hardware in the first place, because the technology changes every year, so it makes a lot more sense to target server hardware that doesn’t change often and can collect data from thousands of users, rather than just one user. Second, the Chinese spy agency would target a phone model that lots of business and government leaders are using. I doubt that the PinePhone will ever be used by anyone important who the Chinese government cares to spy on. The Librem 5 might eventually be used by relevant people, but it will be several years before there are enough apps and PureOS is good enough to attract users who are worth spying on.
However, if you are going to spend the time and resources to develop a secret spy chip for a particular phone model or modem and then infiltrate the assembly plant, you are not going to do all that work for some oddball phone that uses bizarre hardware and software that no other phone model in the world uses. It is simply too much trouble and there isn’t much reward. Also, you never want to be caught, because companies and governments are going to be alerted to your secret trick, so you have to start over from scratch developing a new spy chip that targets new hardware. Why risk all that on a low-value target when there is a high probability of your secret spy chip being discovered in the Librem 5?