Regardless of our personal professional affinities the only reason iPadOS stays locked down is that it's simply more profitable to sell a customer two devices instead of just one. I would love to have an iPad Pro as my only home computer, but it's just not doable due to its OS limitations. The artistic angle is just Apple's way to make the platform believable.
Why would an artist care if I can also compile code on an iPad?
I can only assume that macOS must be offensive to some due to its "openness". The truth is that macOS allows me to be both an artist and a developer, and I don't have a single doubt that Apple could pull off an interface that allows a similar experience on iPadOS. It's just that doing so will lose them money.