I kind of think of wood as I do athletes, some wood has more potential than others even of the same species. I don't think many of us have figured out a way to tell ahead of time which pieces of wood have the exceptional athletic ability but building bows with a lot of reflex will certainly separate the average wood from the exceptional wood.
I have built my share of heavily reflexed bows and in my case I have seen a few different thing happen. Sometimes I don't loose much reflex but the limbs are just a tad rubbery and I don't have as much early draw weight as I would expect from such an extreme design. When a limb gets so thin as it sometimes does in heavily reflexed designs the tension wood can pull it back into shape even though the belly has been badly damaged. Other times I have lost a good bit of the reflex to set but the bow still was pretty hard at brace height and shot very well. I believe that when we are working with wood we are best off to stay within its limitations, sinew backed bows can tolerate much more reflex because the sinew is stretching. I think in most cases too much reflex surpasses the limits of the point of diminishing returns.