Sure it's true. But unless you're going for a naturalistic terrarium setup, is it necessary? I'm not for or against sand for sand boas, I don't really see impaction as that much of a danger, I'm just curious why you use it.

I have always avoided crushed walnut bedding because of the problems lizards have with it. I believe I saw a study stating it was the leading cause of impaction in bearded dragons. And it's quite sharp, I would worry about scratching up sensitive areas.