OS, using AFM-DPI it appears that Boeing use 2.4% at the start of the 2nd segment, but that decreases by the end of the 2nd segment. This is different to your concept of using a MEAN value so that you were above 2.4% for the whole segment.
An old chestnut which has been troubling all of us for decades. In Oz, if I go back 30-40 years, the airworthiness and operational rules took opposing views. In general, the Airlines, certainly Ansett, took the view that the conservative requirement applied .. ie not less than WAT throughout the second segment.
My view has always been that, for an approved AFM for the country in which one is working, the certification is the basic authorisation unless the operational rules are more conservative, in which case the latter apply.
If one takes the view that the WAT limit really is a safety net consideration then, at the end of the day, the main concern is to have the net flight path not less than the appropriate clearance from the bumpy bits. It seems to me that a CFIT is a good recipe for really and truly spoiling one's day ...
OS' technique is a tad conservative and that is his/his airline's prerogative.