It is; the authors appear to be operating in a model where they completely trust app authors and nobody else, though they never actually spell out the threat model (which really should make us view their assessment skeptically anyways), where F-Droid specifically avoids trusting app authors. Nearly all of their objections come down to this single difference.

What echo chamber? I'm not aware of anyone else arguing this position.

That post contains 3 items: One fixed audit finding that only affects initial install of an app, one claim of problems that are unspecified and therefore impossible to assess, and one allegation of poor behavior (which is worth noting but not a security concern).