HEC-2 Split Flow Option

I am currently reviewing a project that has utilized the split flow option in HEC-2 for a super-critical regime. I have used HEC-2 for several years and the split flow option, but have run across a discrepancy in 2 different users manuals. In the "Hands-On HEC-2" manual prepared by Dodson & Associates, June 1992, in Chapter 11, page 11-1, indicates the split flow option may only be performed in the sub-critical regime. Cross checking this information with "Training Document No. 18, Application of the HEC-2 Split Flow Option, April 1982"; I find no mention of this program limitation.

Does anyone have any additional input that might clarify using the split flow option for the sub-critical regime, or is it valid for either regime?