I think there is something to it, but it depends on the smoker and the pipe.
I suspect a few things are going on with ‘breaking in’
1. The briar was not well aged, and smoking it over a few months is actually ‘curing’ it.
2. Forming a cake sometimes improves the performance
3. The wood is no longer being charred
4. The smoker is adapting to the pipe
I have had the experience of buying a new pipe in which nothing tasted good. In fact there was almost no taste. I kept smoking it with mostly Carter Hall to see if it would change. Finally gave up after a few months consigned myself to selling it for cheap. A while later, I gave it one more try. suddenly blends started to taste great in it. It was like somebody threw a switch. During the same time, all my other pipes tasted as they always do. I think it may have finally ‘broken in.’
Of course, it could all be in our heads