Or they should be forced to publicly reveal at the beginning of the game "I have no knowledge of the identity of any alts in this game".
Because I trust the mods not to go looking for it if they don't already know. It's more prior knowledge that is a concern.
With that in mind, the obligation to ensure no game contains a moderator who knows the identity of another user under an alt account should fall
Because only they could know.
So if they have to replace out due to conflict of interest (wincon vs. site rules) or discuss with the alt who signed up a solution that fits both players (can you not use your alt this game? can you not play this game I would like to play?, etc.)
But the burden has to be on the moderation team, and not people playing under alternate accounts.