Thanks to asherkin for solving this problem when it occurred.

It turns out admin-sql-threaded.smx doesn't handle SteamIDs similarly to admin-sql-prefetch.smx which breaks compatibility with Steam64 ID's (i.e. 76561197974481263) and so only works with Steam2 ID's (i.e. STEAM_0:1:7107767).

This makes the core difference whether a players' authority is loaded or not.