No regrets and no negative after purchase sarcasm. Refreshing difference!
That's the way its supposed to go. That's the way it always has gone for me for many years now. That's the way it always will go for as long as you continue to do your research well and select well. As I have said over and over again, if its good it will be good right out of the box and then only get better. If its not then it goes right back in the box. Its that simple.
The changes you describe are the same as I have heard from so many different things over so many years the unavoidable conclusion is everything goes through the same or at least very similar evolution as it burns in. At first the sound is deeper, more liquid, and spacious. It may also be more dynamic but usually in a funny softened sort of way. You have the distinct impression of looking at a truly superb image, and yet are a bit frustrated, kind of like the way Playboy used that soft focus back in the day. Then over time the softness goes away revealing more and more levels of detail- but detail in a very liquid natural way not at all like the grain and etch that so many lesser components try and pass off as detail.
Or as you so eloquently put it:
The tenor of the instrument was real. edgy, grainy in a live sort of way. A profound realism I'd never heard in my system before.
You scored a winner. This is what it feels like to grab the brass ring. Congratulations.