I can tell you from my own experience, the customer is quite often Not the boss!
The gunmaker is motivated by things he hasn't done or seen and by a creative drive that lives in his imagination. I'm pretty sure the M-12 (from reading your book and seeing the rifle, and again THANKS for bringing it to Reno!) was Owen's own dream, would you agree?
The fullstock Springfield that I saw was almost beyond what I would credit a client with conceiving.
If you saw this rifle would you think it was a client's notion?

Truth is, the client had the good sense to ask me what I would like to create, and then let me make this rifle for him. The fellow I'm doing this Hagn for has no idea what I'm up to and just sends some $ when I need it. He's going to get my best, and most creative work. I've radically reshaped the action and am now wet-sanding the stock.

The point is, the maker's best work is quite likely some project he dreamed up and has found a client willing to finance it. My sidelever was such a project, matter of fact, the reason I own and hunt the rifle is because the client didn't like it and traded it back to me.
Often, if left to the client (Terry is a major exception!) they will say, "I want something completely different, just like that one!" And that may be why so many Owen rifles look so similar. Believe me, this Owen guy had quite an imagination!