It's not about Final Cut Pro specifically. It could be a new app. It's about having a single showcase complex app that says to developers—look hey we can build something really performance intensive and sophisticated in SwiftUI. We're dogfooding it. Look what can be accomplished with it!
It could be anything—Final Cut Pro, Logic, Pages, Numbers, a new productivity app all together. Some showcase sophisticated, complex productivity app to show what can be done with it and we're in the trenches with you using it.