I think the best advice any of us can take is just support the damn fixtures with grid wire. If anything call AHJ and ask whether they want two corners supported or all four. Any large commercial, or retail stores, I have done AHJ has always wanted 2x4 lights supported . I even wire the exit ceiling boxes.
I have done two corners, and sure as hell inspector comes in and says "All four sparky" Or I have done all four and the inspector says "wow, I never see anybody do all four"
