Would you care to elaborate on why a better action would be needed for SA voices in the Tyros? Especially given that SA voices are in current TOTL PSR's, with no improvement in the action for them...
Thing is, examine any Yamaha keyboard in the same price range as the PSR S950, why do they get decent actions and ONLY the PSR gets the BOTL action? I'm afraid you can't persuade me that a modern Yamaha WS is any less complicated than an arranger. So how does the Combo manage to afford the decent action and the PSR doesn't?
Other than, maybe, pure profit?
An arranger is just a tool. What matters is what you build with it..!