To clarify, I'm not as confused about the 0.67 factor on U2 as I am with the varying load case strategies (one combining horizontal and vertical in a single load case and another using SRSS).

But I agree that SRSS method seems to be the more "proper" method, despite the extra numerous load cases to do the SRSS math.

I was mainly curious that, since the stress works out almost the same for both methods, why you may use one versus the other from a pipe displacement/restraint load point of view, since that is the only thing that's significantly different.