I don't know the commercial products, but ask yourself: "sure, it's coarse and gritty, but is it coarse ENOUGH?"
Whatever you buy or start with, you'll have to grip a handful and decide whether to make it drain faster (yes) or hold more water (for succulents, no). I think that killing a few plants is how most people learn what "feels right".
I think that starting a succulent out with "too-fast-draining" mix is no problem, because you can fix that by just watering more often. It might annoy you, but the plant will be happy. And if you go too far, the palnt will only slow down until you re-pot it.
But if you start it out "holding too much water", you won't have to water it very many times before the roots rot and almost kill the plant, before you're sure it needs to reported with faster-draining mix.
I remember that "fast-draining is safer" by asking myself: "Which kills a person or plant faster: being thirsty, or drowning?"
Like "which is safer, to much fertilizer, or too little?" Too much fertilizer kills in confusing and hard-to-interpret ways, too little will slow the plants growth and make it send up a message with yellowing leaves. Recovering from too little fertilizer is just adding a little more fertilizer. Recovering from fertilizer burn is probably best done by buying or starting a new plant and starting over.
Adding coarse grit like #2 chicken grit, or Perlite, is a very widely-followed practice, depending on how fast-draining your starting mix is. Very coarse sand, if you can find it, is great, too.And they never break down, so you won't have to re-pot until it out-grows your pot.
I haven't yet found "coarse sand" anywhere that had less than 50% fine and medium-fine sand.
But "crushed stone" can be the correct, gritty, around-BB-size-or-a-little-smaller size, without a whole lot of fine and medium sand. But you might have to buy the more expensive double-screened crushed stone unless you screen it yourself, or if your mix can tolerate adding as much sand, powder and rock dust as your particular bag of crushed stone contains.
But I don't like any of that. I have a major bark fetish. Conifer bark, pine fir or balsam. It is super cheap, and it CAN be found dry and clean/ But I have to screen it myself, which (sigh, sob, NOT!) requires that I fiddle around with it.
In fact, if you start with clean bark mulch , the coarse chunks you reject can become mulch in an outdoors bed, the fines can be a soil amendment outdoors, and the middle grades can either lighten or "wet down" a mix, depending on how fine you screen it. Or you can run a (clean) lawn mower over the coasre rejected chunks, and re-screen those to harvest the finer stuff.
Cheap bark won't last as long as grit or Perlite, but it lasts much longer than coir or woody shreds of the same size. Even coarse bark holds a LITTLE water, and it rehydrate MUCH easier than peat after drying.
Did I mention that bark is really cheap? And long-lasting?
But most people use Perlite, grit, or sand to lighten commercial mixes.
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