Torque loss with a universal socket?

I do not believe you would add to or subtract from the length of the torque wrench by using a universal. I believe it would just reroute the force to a different plane. (sure there could be issues with twist like a straight extension) but unless you bound up the joint I dont think it would be significant.

a bigger issue IMHO would be the calibration of our wrenches

I bet if all of our torque wrenches were checked for calibration we would find then all over the place. but probable in a relatively narrow band (set to 100 but is 95 to 105)

found this... Torque Wrench Accuracy + Calibration | TEKTON® Tools