My only question is why Boeing is not providing the data or not openly stating a prohibition against the higher settings at higher weights
I'm speculating only, but ..
(a) the OEM provides what is required for certification
(b) in addition .. some extra stuff which will sell lotsa aeroplanes
(c) in addition .. additional extra stuff for which the commissioning customer pays a princely sum
(d) the early 737 archaics were intended for back blocks flying which generally entails shorter strips but not necessarily paddock ops, ergo, no fancy additional data either for super short or super long runways.
(e) there is no prohibition, per se, it's just a case of someone has to pay for the stuff to appear in the AFM if a particular customer wants to do something different with the aeroplane.
In the meantime, one uses the existing AFM data to advantage within the limitations inherent in those data.