My guess is they don't. I don't think a lot of wholesalers hold onto their anemones long enough to do so. I don't deal with Quality but a different wholesaler, and they told me about a year ago, in order to get their carpet anemones ready for shipping, they would "fluff" them. From my understanding this is just taking the anemone by the hand and bouncing it up and down underwater. My rep told me this helps stimulate the anemone to close its mouth and get ready for shipping.
Most wholesalers I've dealt with over the years, of which Quality was one of them, have had a hard time identifying the correct species. All the wholesalers that I've been to, most of the employees aren't hobbyists, they're reliable employees. If they are hobbyists, they're usually employees first, if that makes sense.
I guess what I'm getting at is, at their price point, to take up space and employee time, it probably doesn't pencil out to treat an anemone to them. Not to mention, the amount of animals they see and go, would really make it difficult to keep track of treatment. I imagine, as soon as they get the animals unboxed, they go up for sale.
Just my 2 cents