That's not how Ubisoft felt this generation. Or how PC developers felt regarding PC/Xbox development.
Unless systems are generational apart in terms of capability, the porting process could just as easily be done in one direction as another. Developers haven't needed to cut out entire parts of gameplay unless they went to the GBA this generation.
IMO, If I was making the business decisions, I'd tell my people to do the best work on the most successful system, because I'm in competition. If my stuff isn't up to snuff with the stuff on that platform, I'm gonna get waxed and my portfolio of games is going to look much weaker in comparison. I do recognize the need for multiplatform development, especially in these days of escalating development costs, but many here should recognize that many of these decisions are based off of financial concerns and not just technological ones. And different developers choose different things. (Ubi vs EA, Valve vs Activision, etc).
There is no simple and all encompassing answer here.