Do solid wood ukuleles "open up" over time?

To be quite honest, when I first heard people talking about their solid wood ukuleles and/or guitars "opening up" or "breaking in" over time, I thought they were all nuts!  Well, now that I own a few solid wood instruments, I'm starting to rethink my position.  The tone of my solid wood ukes seem to have improved over time (at least the new ones in the first few months that I owned them). 

As I researched this a little bit I quickly deduced that no one really knows if they really do open up or not. 

In this article on the Jumping Flea, Ian Chadwick tells us that the wood actually changes it's tonal effects and density the more it's played.

"As an instrument ages and is played, the wood will actually change its density and tonal effects. This is sometimes referred to as 'breaking in' or 'opening up.' Most often this will result in richer sounds, with more complex overtones in the mid range coming forward. In general, an instrument will benefit from being played and will improve its sound with use. So if you don't like its sound now, keep playing and you may like it in the future."