Dorico and, I believe, Wavelab use the Qt cross-platform framework (not to be confused with Apple’s QuickTime, which provided the underpinnings of the legacy Cubase and Nuendo video engine). My understanding is that Cubase and Nuendo do not use Qt; I don’t know if they use another cross-platform framework or platform code that Steinberg developed themselves. This failure to use a well known cross-platform framework means there is no independent information available on performance and it is unlikely to be as simple as upgrading to the latest version of the framework.
Much of the implementation of user interface code for OS X and Windows differs, not least when it comes to HiDPI support. This can lead to quite stark performance differences even if the same graphics hardware is used on both operating systems. It sounds like there is scope to optimise Cubase’s graphics performance on OS X.