That flag is the result of clicking on the "Web" tab of the results page, so it kinda is a documented feature. All the tabs have their own udm value (e.g. image search is 2, AI mode is 50, etc.).
When I'm working on a repository where the remote is shared (like a corporate GitHub repository where not everyone has their own GitHub fork) I tend to name all my branches like 'eru/'. That way I can quickly find my work, and I can also confidently delete branches without worrying about stepping on other people's toes nor being stepped on by accident. I encourage co-workers to do the same, but haven't strictly required it from team members.