It is possible that the data is leftover from me2. When I get a bit of time I'll run that variable through my data dump to see where it appears. Maybe it's in code somewhere.
Edit: This appears in SFXGame in SFXGameConfig.bShieldsBlockPowers. It is marked as coalesced so editing it there should have an effect.
The code where it is used is from Patch_SFXCustomAction (powers mainly):
You could possibly patch out in the if statement by figuring out a way to replace bshieldsblockpowers to either always be false or always be true. But it should be overridden by bshieldsblockpowers (it has coalesced flag on the export), but those otehr things like hasanyshieldresistance() may make it not work like intended.