I've done T-5, 4-tube low-bays before and I seem to remember the white & grey ballast lead connected together at the factory with a push-in connector and a lead coming off to connect to the neutral of the supply
Is this correct?
I saw another brand that has black, white and gray, but they show the supply neutral connected to the white ballast lead, and also feeding a switch that connects the grey lead to the whites.
Is this just to switch 2 of the lamps separately?
If so, why is the switch loop in the neutral?