In my opinion, there is a difference in the change in momentum and impact load.
Note that the two effects will have different force orientation.
It may be that change in momentum to be important, but in my opinion the impact is more critical.
Slug will hit the elbow (impact load) so the calculated force will need to be multiplied by DLF so will become the governing factor.
Anyway if your design is ok with a DLF x Force straight to the elbow, then will be ok anyway.