but that either applies to GrapheneOS as well, or there actually are trustworthy alternative ROMs out there. GrapheneOS being one, /e/OS being another, for example.
there are more that i am less familiar with, so i can't talk about them, but /e/OS is run by Gael Duval, who has been running a Linux distribution before that for many years. and even tough there are criticisms against /e/OS including the claim that it overstates its security and supposedly hasn't removed all google connections, i will trust Gael based on his reputation far above anything coming from google. even more so compared to other OEMs who stuff their android versions with bad apps that you can't remove.
so no, i am not trusting a random guy on the internet. i am trusting someone with a known reputation, someone who i have actually exchanged private messages with, someone who i could even meet in person if i were to come to the right conference.