I think it's just a function of hundreds of players (maybe 1,000?) not even having a profile yet since it's only April 29th. Once we reach signing day, I'm guessing there will have been maybe 350 players added who will rank higher than Anderson.
Last year, Anderson's composite score (.8416) would have been the 1,334th on the list. So once all of the players are added and ranked, he'll slide down around there.
Worth noting: ESPN has only assigned a ranking to Owen Anderson and Joey Okla. So once they evaluate the other six, their composite scores will either climb or tumble. Rivals hasn't ranked Boyer, so he doesn't really even have a composite score yet. So a lot of these will move.