4k+ now should just mean they have pretty much all slots filled with 25M gear, doesnt necessarily mean its optimized what so ever though. Gearscore is garbage when people try and use it at some elitist tool, but fine if its just a general "oh.. you're relatively in a range of what you should be before you do X raid", so shitters like tanks that join a raid without defense cap dont get invited. (this has happened in half of the raids ive done since launch so far lol).
Unless it changed since back in the day, people would just pad their gearscore with shit they wouldnt even use just to inflate it due to the higher ilvl and stats, then swap back to what they usually wear.