
The sampleset producer decides which of their native controls can be affected by Hauptwerk's registration tools (generals, stepper frames, scoped, reversibles,...). I don't have that particular sampleset, but have fought with various native controls like Anches ventils that do or do not respond to Hauptwerk reversibles, for example, differently across samplesets.
One trick is to override your general 10 (or stepper frame xx9 or x09), which I assume you've autodetected for all organs, by autodetecting the same physical piston to the Tutti button on this particular organ. Same for the PP, P, MF, and FF. That won't mess up the generals (or stepper frames) for other organs. There's a relevant General setting in HW 7 to override global MIDI associations locally per organ (rather than trigger both the general and the Tutti), but I can't remember the name of that right now.
Got it: Check the option "Organ MIDI assignments override global" in General settings | General preferences | Main 1.