If I recall correctly, sqi were originally created to boost woe/pvp, (the staff who originally created sqi used this thought process). So when TF was originally designed, it was boosted for damage against demi (players) and insect (which, at the time, was emp property, although now it's holy, and we've changed TF to reflect that, although apparently I've forgotten to update the description).
That should answer your questions, past staff boosted the sqi for pvp/woe purposes, not for pvm, even moreso for something like TF, when sinx have so many other options, and a leveling sinx might choose a DDB_ dagger for aoe purposes.