Thanks, that's helpful, you lay out the foundation and underlying reasons for short vs long proofs, and the use of the commercial yeasts vs home-grown ones. It seems then, that the purpose of omitting the second proof is to remove the flavor component of the yeast/flour/sugar interaction, and then let the ingredients themselves come through. I thought it might be more texture related, too. This is where I shrug and say okay?
And thank you for the new term: " viennoiserie" 
That is precisely what I plan to explore this winter!
Slight tangent, and going to explore path of croissant vs kouign aman, as that's a fairly easy comparison for me to capture.
Earlier this year, I had a modicum of success with making croissants that used a combination of yeast and sourdough, but was distracted by something else before I could explore further. Many recipes also suggest using an osmotolerant yeast, which I've researched and understand it helps speed up the process a little.
I've read that croissants may leak when baked if not proofed correctly (i.e. leak if underproofed; also, understood there may be other factors contributing to the leaking). How does this, then, work for recipes which call for minimal or no second proof, such as the kouign aman? Is the leakage somewhat desired in this case, to "fry" the dough a bit with the sugar? Why is the proof time in some KA recipes removed? Is it to reduce the "chewiness" that could be caused by the extra salt and improve the tenderness of the dough, or to bring more focus onto the flavor of the butter, sugar, and salt? Am I splitting hairs? These questions may simply not have an answer and be rhetorical, and I may just have to run my own tests to see why. Of course, baseline recipe first to have a standard to compare to.
