I guess I expected on the homepage or maybe "About" but I was looking for something related to whether you open PRs on my behalf given that OAuth prompt.
I think adding that or some explanation during onboarding about the permissions might help.
Again, I understand that this would limit me to scanning public repos, but that would be fine.
Using an alternate auth provider won't even prevent you from scanning non-public GitHub code. There's a GitHub OAuth App just for auth (which is what you're seeing here), and a separate GitHub App that you need to install either way to give Detail access to the right repos. We can swap out the former for Google/Okta/pw if you want to avoid this warning. GitHub Apps (the half that manages repo access) have a much finer grained permissions model.
It would make a lot more sense to me if you provided a lighter "intro" version, even if that means it can only run on public repos.