Axios I see the radical difference in the page logged in vs not logged in but I don't think that's your issue.
When I'm logged in I get all the posts but not with your uniform "a few seconds ago" thing.
I would guess that's a Flarum thing...or the way the browser and isp are communicating.
If this is an ALL THE TIME thing I would reset universal time, flush dns maybe, housecleaning, reboot, reboot.
If this is intermittent then it sounds Flarum-y.
For me sometimes, at least 1-2 names, in your picture, will say deleted user instead their name
