Is this really a factual statement? In all cases?
This is marketing copy to sell a product to Beesource readers (in the sponsors and vendors forum). A product that is illegal to use in the United States. Making claims that simply aren't true to sell the product is crossing a line that shouldn't be crossed.
You will notice that no one else that sells vaporizers makes such a claim...there is a reason for that.
Even if you have some brood, you can treat. OA will not harm either the brood or the queen. However, it will NOT kill any mites that may be in the brood.