I just noticed that if I'm signed in as an admin and I select a specific user from the second dropdown (who is not an admin) and select "All types" in the first dropdown, the results returned are not filtered; it displays other actions made by other users as well.
After more testing, I realised that this happens only for some specific users. After trying even more, it seemed like it is a bit random, I guess. It happens for some users of role x but other users of the same role doesn't happen to them. Some times results are filtered and other times they are not. Not quite sure why. I have custom user roles, if that's related.
On a side note, whenever I open the select dropdown, the results area disappears for a while and the loading spinner shows up, then it returns back to the results again. This happens before I select anything from the dropdown (it's still open). Shouldn't the loading/filtering only happen AFTER I select something from the dropdown (i.e. onchange)?