OH - you mean "front loading" in the sense of "before the die roll instead of after". I was thinking of "front loading" meaning "before the combat happens at all" - as in during character creation.
I guess I can kind of see that version of front loading being beneficial in that you only need to do it once if you do it that way. Except that's not how we ever used THAC0. Before we figured out how to use ascending AC (probably 10 years before 3e came out at least) we always subtracted our roll from our THAC0 to calculate what AC we hit and then told the DM (so the AC would stay secret until we figured it out by which rolls hit or missed). So we were doing the math after every roll with THAC0 anyway so no front loading there for us at least.