More accurate? No, because accuracy is in the archer. What I think we mean to be talking about is precision, and I think that a properly tillered bow will be more precise, but not more accurate. The concepts of accuracy and precision are closely related, but not the same.
I believe it should make a difference for the same reason that has been stated above. Proper tiller will make the bow more consistent over time, and will reduce things like hand-shock. All of those little things that it contributes too should make a properly tillered bow more precise.
All that said, I don't believe that the beginner or even the intermediate archer would notice the difference in precision because it would be too small and would fall well within their own margin of error. But for the expert shooter, who is already consistently accurate, that small difference in the precision of their bow will make a difference because their margin of error is so small that these minor issues can make significant differences.
If you are shooting a 12 inch group, proper tiller may only make a difference of a 1/4 inch, which means nothing to that group in practical terms. But if you are shooting a 2 inch group, then all of a sudden a 1/4 inch matters a whole lot.