From what we have seen, the answer to this question is yes and no. Yes, the hydration level can impact yeast performance, but once you reach a plateau on absorption, generally speaking about 56 to 58% the effect of additional water in minimal, but what you see is a softer, more fluid dough that responds to the byproducts of fermentation (alcohol, carbon dioxide, and acids) to a much greater magnitude than it would at a lower absorption. IE, the softer dough expands more readily, gets bigger faster and appears to show the effects of greater fermentation, but it's just the softer dough that you're seeing, not more or faster fermentation. It is really pretty complex and would take a small book to do it justice, so this is just a very general summation of what is happening.
Tom Lehmann/The Dough Doctor