Trust is a very personal (and situational) thing. What counts as a ‘good reason’ for you and for someone else won’t necessarily be the same. This is one reason why it is useful to acknowledge when a privacy measure is not purely technical and is based on trust or shifting trust.
I don’t think this is something that anyone needs to be getting defensive about (not pointing at anyone specifically just my impression of the overall tone of the thread), shifting trust isn’t a fully verifiable or technical solution, but it is a practical solution to various privacy problems that can’t be easily solved in other ways. A VPN shifts trust, a private search engine shifts trust . The goal is to shift trust from a less trusted to a more trusted entity, when a trustless solution isn’t practical. And the reason it is important to be clear about that is because we all have differing levels of trust in different entities, and because we don’t want to give less informed users an inflated sense of confidence (common problem with VPNs for example).
Realistically with GrapheneOS, I’m sure that the vast majority of people who choose to go out of their way to install GOS would much prefer a GOS proxied connection instead of a direct connection to an untrusted 3rd party service. Proxying connections in this context is a good thing in my eyes. But that doesn’t mean people shouldn’t be aware of the trust relationship and the inherent theoretical vulnerability that exists.