I’m not sure (Reaper has a stronger endgame than Possessor, but is weaker early on and in the midgame), but either way, NKs as a whole are underpowered, so even if he were the best that would be damning with faint praise.
But either way, this is a very minor buff that would mostly just prevent Drunks from randomly finding them with one visit. Since NKs are a solo side, and since they’re supposed to be a major factor in the game, it shouldn’t generally be possible for a single visit to decisively identify them. (And being identified by the Drunk is particularly bad - Drunks can prove fairly well with their will, and can also use HH to shut you down for a while even if nobody believes them.)