I think that the legal aspects rather lie on the camp of greediness, selfishness, egotism and opportunism
My guess, truly, is that artists are generally "coached" by their business advisors or may not even know this aspect of an agreement. I have been around and done a lot of sessions and I have never heard a guitarist, ever, say - you can't see my amp/guitar/whatever settings lol.
However, sound folks, engineers are very different and many times they are secret about things. I am not sure in the case of a modeler why it would be a big deal to the artist or the digital supply company - unless there exists an agreement and then it would be the legal and business folks "protecting" the artist and the supply company from any exposure.
I understand why it happens and yes it does, even though it doesn't seem correct. Paul Gilbert would mark his pedals where he wanted them and he would show you and say "go and mark it right here." As I said - I have my opinion which is more like Paul's.
As an aside, I got scolded by a sound engineer one time when an audience member asked how I was mic'ing my cab. In the first place, as a guitarist mostly, I didn't really know or care. In the conversation, I told the person it looks like it is x,y,z off center of this x,y,z speaker. Complete bla bla bla guitar head talk. Afterwards, the FOH manager had words with our management. And so it goes....
The only reason this is now an issue is because a "digital" file of a rig can be saved and so some snarky lawyers, business managers, and others can go "that is our personal property." Why because it is now "digital"?
Last I knew that was a digital copy of what a physical device could be set at.
Maybe the actual digital file is, maybe it is not. To me I never heard anything about treble, bass and mid and amp settings being copyright material.
However, I am sure someone will learn to make money off of it.....if you get a judge to agree...lol.