Chau, I'm slightly confused. Could you clarify what you mean by a "dry looking" crumb and how you think "overfermentation" is responsible for lack of moisture? Are you suggesting that greater gluten breakdown from over-fermentation resulted in more moisture loss during baking?
I think when you have overfermentation you have a couple of things going on. There are enzymes breaking down the gluten matrix releasing water and actually making the dough feel softer and a bit more wet. The dough will be harder to handle and feel more slack. But the resulting crumb structure is anything but moist.
I'm not sure if during the bake the excess moisture is released because it's now free, but the crumb is definitely more dry to the touch and taste. Part of the toughness of the dough is also due to the excess acids produced during overfermentation. This has a strengthening effect on the gluten strands. Again this isn't due to overkneading and/or a low hydration which are 2 other sources for tough dry crumbs.
As a result, an overfermented dough has less oven spring and a slightly tougher crumb. The greater the fermentation, the tougher and drier the crumb will be. I know you can't taste the crumb through the computer but if you study the crumb structures carefully it is quite evident what I am referring to. This was one of the first same day doughs that this has happened to me. This was purely caused by several reasons. One being that I proofed the dough at higher than normal/room temps in the microwave b/c I was impatient and wanting to bake before it got too late. Obviously when you proof at higher temps, the window of screwing things up becomes smaller. I let it stay in too long. The other reason is that I had about 5 hours from start to finish so I added too many sources of yeast to this dough.
Here are some better crumb shots of similar pies. These were just as airy but also moist and tender and no hint of dryness. These are taken from various pies and different sections of the crust. Some of these are actually from the same pies despite looking different. I want to clarify that these are not tartine pizzas. For the most part, they are just some crumb shots from same day pies.
Sorry about hijacking the thread, just wanted to clarify with some pics.