I totally agree with your opening post. Both the company and the AOA seemed to be using the RDO, shamelessly, as a fig leaf to hide some fairly predictable agendas.
I suspect the RDO is part of Hong Kong's policy of localization, so to that extent it is perhaps admirable. However, as you point out the intent of the RDO may be one thing, but the wording is quite another. One phrase that confuses me is "existing contracts". The company seems to be playing upon this, in that contracts awarded before the RDO are fine in their eyes, however new contracts (ie New Joiners) are not and therefore, reluctantly
they cannot offer expat terms to them... how convenient?
Putting all that to one side. How can the Cadet Scheme be deemed to be organized along racial grounds and therefore fall foul of the RDO? Examination of the scheme, in both word and deed, show the cadets are, by design, not selected along racial grounds, nor is the system rigged or fudged that only one racial group is selected. They are indeed a racially diverse bunch.
The final sentence of your opening posts appears spot on to me FWIW.