This is correct, according to the tournament information, only players who had played for a team were locked to that roster. Teams could add more subs if they wished
That one breaks my heart though. He's been such a huge part in their success, not sure how they'll fare now that they have to replace a main pillar of their comp.
Seagull might have been included in their roster beforehand too (since I'm sure they've had this figured out for awhile now) and nV simply asked it to remain private until they were ready to release it.