This is also a good point. Even if we were to assume that no optimizations were made to these apps, there would still be competition from actual native iPadOS apps, unlike if you just replace iPadOS with macOS, which would just leave a ton of Mac apps which aren’t optimized for touch.
Here’s a simple use case actually:
Given the exact same company: Adobe. And the exact same app: Photoshop.
Given that users can run either the iPad version or the “desktop Mac version” of the app on the same device, most professionals will simply just use the Mac version because it has more features and is more powerful. The iPad one is very basic and limited. And fundamentally there’s not much difference since the Mac version also does support pen input and touch input.
This will basically happen to every other “pro” app as they are right now.