I don't see anything they offer for security that's not also in AOSP/LineageOS/eOS/stock/etc.
Which is not to say that's not enough for most people, but why highlight them? It doesn't seem comparable to the laser-focus GrapheneOS has on security
They look way more trustworthy.
Not GP, but Volla phones are cool in that they officially support running proper Linux[1], so you could just use Linux instead of Android if that's enough for your needs. And you can still boot into their de-Googled Android if you need to run Android apps.
[1] https://volla.online/en/operating-systems/ubuntu-touch/