Can't say anything for the impression you get from the style but I can at least say that GrapheneOS argues different things and differently on quite a few of the points made about F-Droid. They have also always been big advocates for open- source Android apps and explored/implemented F-Droid integration in their OS at points in the past.
I'm familiar with the PrivSec people and they are different from GrapheneOS with a tiny bit of community/mod overlap. There isn't any GrapheneOS dev presence in the PrivSec project.
I don’t think this page is affiliated with GrapheneOS. See https://privsec.dev/about/