By default, smut is optional but allowed. Prefacing a freeform tag with "Smut" means that smut is required to fully complete that tag, just like any other element of a freeform tag. If you would only be happy if you received smut, you should nominate a smut version of your tags and request only those. Otherwise, you should/can request tags without "Smut" and you may or may not receive smut. I hope that helps!