That particular flow defines some of the required compensations between an RTOW chart and reality (whether or not is the chart smartly configured to match the operating conditions) and a couple of validity checks (Vmu, min V2, dry/wet). What I called 'some other bits maybe OEM specific' in the post above.
Needed, but only a small stop on the path to understanding. Just a note for other readers not to get stuck looking into the picture for something not on it.