Toe out would just add drag. Plus, it would generate low pressure pulses on one side in straight & level flight- just like a wing at high AOA & this would finally snap off the SFG. SFGs add stability in straight & level flight by acting like additional rudders & add rudder authority in KE.

SFGs arent new. Most of the Airbus and Boeing airplanes have had them for over a decade. Just look for the wingtips on these airplanes- Airbus has flat wingtips just like SFGs where Boeing has tips that curve upwards. Both have the same function

Ameyam