I think it's quite simple,
* if you are a more casual user with strong security and privacy needs, then the Linux phone distros are not there yet. Use something else.
* if you are a Linux enthusiast/developer/hacker who is interested in getting away from Google and Apple eco systems, consider getting involved in one of these Linux phone projects and helping out there.
This should not be seen as competition, it's all free and open source software. Android hardening projects focus on delivering a reasonable solution today while Linux phone projects focus on getting something truly independent in the long run.