I have my own little theory about this, and I don't know if it right at all, but it something like this:
Since most of the notes I find in a finish seem to derive from the cask, such as wood, spices, leather, peaches and apricots, nuts and marzipan and so on, I think perhaps the quality of the cask has something to do with it.
When a cask is used that is well used (2:d and 3:d refill) and is 'dead' in the wood so to say, the finish will become lesser. And with an 'active' cask the woodimpact will make the finish more intense.
My theory explained simply...