Well, this isn't really a bug. The user is editing from mobile, the AF block happens within the same session, which is again on mobile. The block creates a RC entry, and MobileFrontend correctly recognizes and tags it as "mobile edit".
The real issue here is not having a precise way to identify system users (something like r481601), so MF could avoid tagging the RC if it's for a system user. But aside from that, I'm unsure whether the AF block having the "mobile edit" tag should be considered a bug...
I think the solution here should be implemented inside MF (and not AF). That's because deciding whether to add a certain tag to the edit of a system user strongly depends on the tag itself. For instance, the PHP7 tag would be fine, while the mobile edit tag could be confusing.
Ideally (as I said above), I believe we should have a way to identify system users, and then MobileFrontend (or any other extension adding this kind of tags) should change its RecentChange_save hook handler and abort it earlier if the user is a system user.