Interesting perspectives, some true & some only half true. I can only speak from my own experience and education, so somebody who knows more about it may think I'm only half true as well.
You must first consider genetics, and/or species. Hard maple encompasses a few trees, mostly of which is sugar maple. Black maple is nearly identical as a tree, and virtually identical as lumber. The trees are so similar that they naturally hybridize. However, the catch is that red maple (soft) and black maple also hybridize, but red maple & sugar maple do not. The hybrids of either can & do mix with others, either way, though. As much as I know about each tree, I even get confused when walking in a mixed maple forest as a tree may be on the softer side but exhibit leaves & bark that more resemble a hard maple. So basically, you just don't know until the tree is cut, milled, and dried. If it's hard enough for cues, then it's good. If not, then it's a waste.
Drying the lumber is another issue, as stated by Vince. I personally prefer to dry maple at low temp, then heat it after the fact with steam to relieve drying stresses. My lumber begins it's kiln drying the same day the tree is cut, usually within a couple hours. The dried wood will be the same color as it was when cut. Older trees with almost no sap wood will produce brown wood, not to be confused with lumber that was overheated in the early stages of kiln drying, or from logs that sat around too long before milling & drying. Younger, healthy trees produce the bright white wood, but that wood can be dried improperly & turn brown. Drying is as important as choosing the correct tree.
Old growth technically means the wood came from a 150+yr old tree. That's not old for maple. Most trees I cut are in the 80-100yr range, with 150+ not being uncommon, depending on the tract I'm cutting from. What many folks think is old growth is the stuff being pulled up from the great lakes. Unless the guy is there to count grain lines on the log, there's no way to know if it's old growth or not, regardless where it came from. Brown wood doesn't mean old growth, either. In fact, only the 250+yr old trees I have ever cut produce a majority of brown wood. As the tree grows, it's only the outer layers (sap wood) that are alive, and growth comes from an extra layer each year. The wood in the center is dead (heart wood), and with time will turn brown. I have cut numerous old growth trees that had tiny hearts, meaning lots of white wood. You can't tell in shaft form.
Things I consider when choosing shafts include hardness, stiffness, uniformity of color, weight, and most importantly tonal characteristics. There's a happy medium of each factor that creates as perfect of shaft as can be had. Each taper & dimension will require a different specification to be optimum, so it's up to the individual builder to find what works best for his cues. What works on my cues might not be any good for Joey's cues, simply because our taper shape & dimensions are different. Chances are pretty good that a piece of wood that's good for me, would work on anybody's cues with satisfactory results. But it's likely not the best, unless their taper is exactly the same as mine. And then you must mate the shaft with the butt. Each cue butt will have its own tonal personality & you must know how to match a shaft to it to achieve optimum performance. It's a delicate balancing act, a science for sure. That's not to say a guy can't build any ol' butt & use any ol' shaft and produce a fairly nice playing cue. It can & does happen. I'm just saying that it coulda been better if he'd have taken the time & matched his woods.
So in the end, I guess old growth doesn't matter. Each tree, like each person, is completely different. Some old guys are wise & have priceless lessons to pass on to us. Some old guys are idiots. Trees are no different. Judge each shaft individually, regardless of how it's labeled. I can show you a shaft with a zillion grain lines & brown color that came from an adolescent tree, and another shaft with white color & 6 grain lines that came from an old growth tree. It all depends on a mix of genetics, history, and growing conditions, then how long the log sat before being milled, how it was stored during, and the manner in which it was dried. There are too many variables to consider. It's easier to just know how to pick a shaft for it's quality rather than some special label you can stick to it.