Yes, it appears you do have to leave before 7 am, I'm guessing it's geared towards employees who have to be there early?
Transit Payment Center to Carowinds, SC - Google Maps
Checking again, it doesn't go BACK to uptown except for right after it drops off at Carowinds in the morning either. Doesn't really make sense to me to not pick up later if it is geared toward employees. Hopefully someone else on here will know more.