The account committing changes is not the same thing as who is developing or reviewing it. Look at any of the most active repositories like frameworks/base:
https://github.com/GrapheneOS/platform_frameworks_base/commits/15/
The account GitHub lists as a committer is the one which pushed the changes via Git to GitHub or which pressed the rebase and merge button on the pull requests. It isn't the author of the work.
Look through pages of the commits there. Who is doing most of the work there? Not the person you said.