Still don't know if there's a rule or not. I didn't ask and applied "Just do it and ask for forgiveness later."
And for all of you who have your head in the gutter, lol, I was thinking more in terms of efficient use of the shower suites for everyone -- why use two if not needed, especially if others are waiting?
The shower suites are a great amenity after a TPAC and especially while waiting for a connecting TCON.