Yes, I think that's right. The Supreme Court, in its order, spoke of a “competent adult person”. I don't think it would be open to you, for example, to have 16 as an age of consent for this purpose, because that would not be a competent adult person. Between 18 and 21, I would think you would have some leeway within the word “adult“ to decide that.
On January 25th, 2016. See this statement in context.