It makes no difference in Sport Mode until a very high-speed is achieved in D, then pushing to DS will downshift behave like a OD button again it depends on speed.
However, it makes a significant difference between D and DS in Comfort Mode, higher shifting point is achieved in DS.
When the Sport Mode has been selected, the tranny already strated working based on its sports program; that derives the "Sport" so there is no such thing as "Sport Mode with normal transmission" and it's also not logic to have responsive throttle without sport transmission program. Try as you may... Cheers..