There's no accounting for all the minute differences that will distinguish two seemingly identical guitars - the exact pieces of wood and the way they were cut, any minor tweaks the luthier makes to a design over the course of years, etc.
But we've never had a better opportunity to hear what time and years of playing can do to change the tone of a guitar than we do today. We briefly and very serendipitously had a brand new Bespoke Kostal OMC in koa and German spruce at the same time that we had a pre-owned 2018 OMC in the same tonewoods. We lined them up and played them side by side, and were struck by the results. If ever you've been skeptical about the obsession with "played in tone", this may put that to rest!