Rock-It Man's research is correct, thats because the E-Diff doesn't require a friction modifier, the clutches are located in a separate circuit that uses automatic transmission fluid to control clutch engagement levels. In a standard limited slip spring pressure maintains clutch engagement until axle rotation overcomes the friction, modifiers prevent the clutch pack from chattering. the E-Diff can engage the clutch from 0 - 100 percent or anywhere between via separate computer controlled hydraulic circuit so no chattering. That said having it will likely not cause a problem but it's not required as the clutches are in another housing. Mobil1, AMSOIL and Royal Purple all make excellent 75W-90 without the additive, GM sources it's gear oils from various suppliers. I use this with excellent results on my 1LE and Sierra's locker.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1