As an individual, blocking people who tax your mental health is healthy. As an app developer, blocking people who try to report security issues is problematic.

Releasing an app doesn't make somebody somehow not an individual.

There is a difference between blocking people who are disruptive, annoying, etc. And then blocking anyone who doesn't agree with you or levees any amount of criticism of your work. At some point surrounding yourself with only yes men will become unhealthy.

No, there clearly isn't.

GrapheneOS was not blocked by the developer / project as far as we know.