There's zero way to look at a shaft's grain count, cleanliness, and straightness of grain and know whether it's good or not. The only thing you can deduct from a shaft's aesthetics is whether it's pretty or not. I have seen my share of pretty junk, and ugly gold. It's not the rule or the standard, just an observation. On the flip I have seen it in reverse as well. Point being, a clock is right twice a day by default. In my experiences, that's about as precise as conventional cue maker wisdom when it comes to choosing shafts.
I REGULARLY use shafts that have wiggle or wave in the grain, just as I do beautiful straight grain. Turns out they stay straight & people play just fine with them. All that said, there is a point where if the grain is bad enough the shaft will be prone to warping and or cracking/splitting when flexed. As a general rule, I want to follow a grain in the center of the shaft from tip to joint. I don't care if it wiggles along the way, just as long as it reaches both points.
Another thing I quit worrying about is grain count. Tight grain vs wide grain means nothing if you weren't there to study the tree it came from. Tight grain could mean anything from a diseased tree to a quite healthy under story tree, drought, lack of sun, bad soil, etc. Once in lumber form, you'd have no idea if it's good wood or not, just that it has tight grain. Not the same with wide grain. Wide grain means the tree had ample sun, nutrition, and hydration. Chances are very good that wide grain indicates a very, very healthy tree. Furthermore, mineral stains indicate rich soil, which usually translate into healthy wood that makes heavy, dense, pingy shafts. And sugar maple has wait for it............sugar! Why would anybody trust sugar maple that has no sugar? Fact is that a good straight shaft can be pretty with straight, clean, tight grain. And it could also be wavy, wide grain with sugar lines or mineral spots. But something you won't likely ever see is a bad playing shaft that has lots of sugar &/or mineral staining. You'd be hard pressed to find a bad playing shaft that only has a couple grains per inch. I know my opinions don't fall into the conventional thoughts, but I have spent the last many years studying, logging, milling, kiln drying, and processing much of my own wood, and things I have learned changed the way I see shaft wood. Take it for what it's worth, which is nothing to anybody but me.