Well for one thing The Greek Freak isn't a prospect anymore. Their criteria look like an attempt to sneak an established NBA star onto a "prospect" list. This is his fifth year and he's an established superstar.So where would folks slot Tatum?
Using their wacky system a superstar in his fifth year is a "prospect" and a third year player, like Willie Cauley-Stein, and a second year player, like Buddy Hield, aren't. If they want to compile a "Best NBA players 23 and under" list, they should just do that honestly.
I would limit any prospect rankings to guys in their first three years, because with incredibly rare exceptions by year four a player is what he is (on the aggregate they might refine their game, but the big leaps in performance are generally over). I would no more consider Andrew Wiggins a prospect than Marcus Smart.
I'll give Embiid a pass as he spent two years injured, but otherwise I'd consider prospects the guys drafted/entering the league from 2015-2017. On that criteria the only guys I can really put over Tatum are Towns, Porzingas, Embiid, and Simmons.