If they come from a fishless system, I agree that its not needed. Just don't add the water they come in.
But I must confess, I qt
them anyway for a couple of weeks. Gives me a piece of mind with my past battles with ich. I once had some live sand from another system bring ich into my system.
That came from a tank with fish hosts in it however.
run copper in their fish system, so they keep inverts and corals in a separate fishless water system all together. Without fish hosts in that system, it is unlikely that they could carry trophonts.