If you perfect this, @toadhall, you might have a winning solution to the problem of heat removal from the DHW tank per the frost prevention algorithm, as eloquently expressed by several users part way through Samsung R32 ASHPs - when is a defrost not a defrost? (e.g. @Michal_S et al). Presumably you could just write a “1” to 0x4089 every 55 minutes (followed by a “0” a few seconds later) - thus sidestepping the frost prevention cycle requirement - if you were sure that a real frost prevention cycle wasn’t required (e.g. if you have glycol in your circuit).
You and @Topaz appear to be well ahead of the field in understanding the Samsung NASA protocol subtleties. Have you considered summarising your combined knowledge into an idiot’s guide?