To 'create' dreads, it's not too bad, unless you do them too tightly. If to maintain them, that's when damage is caused more, because it breaks hairs, so over time, the more you crochet, the more hairs break, until eventually the dread is severely weakened to the point it breaks off.
People who use wax also are very loyal and happy customers, it doesn't mean it isn't damaging, just that people don't see the damage it does. The thing about dreads is that the outside can look perfect, while the inside is a damaged mess, and you can't necessarily tell.
Besides that, it's kind of like palm-rolling; you're doing it to fix something or maintain dreads, make them look neat. And then not long afterwards, they're messy again, because that's life, but also because the thing you're doing to tidy them is causing them to get messy again lol. So damage aside, I think it's pointless, because you'll be crocheting to cover up the frizz and mess caused by crocheting. It's a never-ending battle.