Depends on D20669. Ref T13343. Currently, the user activity log includes a number of explicit administrative actions which some administrator (not a normal user or a suspicious remote address) takes. In most/all cases, these changes are present in the user profile transaction log too, and that's generally a better place for them (for example, it doesn't get GC'd after a couple months).
Some of these are so old that they have no writers (like DELETE and EDIT). I'd generally like to modernize this a bit so we can reference it in email (see T13343) and I'd like to modularize the event types as part of that -- partly, cleaning this up makes that modularization easier.
There's maybe some hand-wavey argument that administrative vs non-administrative events could be related and might be useful to see in a single log, but I can't recall a time when that was actually true, and we could always build that kind of view later by just merging the two log sources, or by restoring double-writes for some subset of events. In practice, I've used this log mostly to look for obvious red flags when users report authentication difficulty (e.g., many unauthorized login attempts), and removing administrative actions from the log is only helpful in that use case.