The math described at that link is correct. Hopefully your engineers know that, and understand that 10A + 10A is not always equal to 20A.
Adding up the totals differently would be wrong, so it is unlikely that you are going to find something to support that.
Transitioning to Revit from AutoCAD and Excel requires a lot of change in your workflows and standards. If you were calculating phase loads in amps by straight addition before, this change makes your calculations more correct. You will be better off changing your standards to match Revit's format rather than trying to make Revit produce your old schedule.