From the Tokyo – gameplay page: (emphasis mine)
Ticketed attendees of in-person Pokémon GO Fest events will have two opportunities to encounter a Mewtwo that has at least Mega Level 1 unlocked*:
Timed research:
[…]Super Mega Raid at Pokémon GO Fest Park
Ticket-holding Pokémon GO Fest attendees are invited to join a Super Mega Raid at the end of their ticketed park session. For the last thirty minutes of the Park Experience, new Gyms will appear that allow over one thousand Trainers to take on Mega Mewtwo together!Both Mega Mewtwo X and Mega Mewtwo Y will appear during this part of the event. Stay alert, Trainers—your help is essential to keep Team GO Rocket away from Mewtwo!
Mewtwo caught from the Super Mega Raids will have a Pokémon GO Fest 2026 Location Background and Mega Level 1 unlocked*!
More information will be shared to ensure as many Trainers as possible can participate.
Be sure to join this exciting experience and leave Pokémon GO Fest with new Pokémon and exciting memories.
*If you’re lucky, it might even be at Mega Level 2 or 3!
It talks about "two opportunities" (one being the research), "a mewtwo", "a raid": singular.
How do you read that?
Could it be that yes, in the last 30 minutes multiple gyms spawns, but that's to allow for that thousands of player interactions mentioned and it will actually be only one single raid?
(maybe that's necessary for some technical limitation and to better distribute people all over the place instead of all in one place. Also: how would one choose which one then? Maybe it's tied to the research you choose, even if that would be bad and I'd like to at least have the option to do the research for one and the super raid for the other)
EDIT: Also it was datamined some time ago that coordinated raids "will need a large number of players to defeat the raid boss." (singular)
by compox