Can't query for @username in comments across public repos

When my username is mentioned in any public repo comment, I get an email notification linking to the comment and providing the comment text, like this:

Why can't I query for this same information using the Gitlab API? Specifically, I just want to query for recent @username mentions in any/all public repos for the account associated with my Gitlab API token (I'm not for try to scrape gitlab for arbitrary user comment mentions, just comments where my own token's associated username is mentioned in a comment).