i know, i went on it.
When you enter the queue there are signs that say "not wheelchair accessible, must be able to transfer" to some effect. Surprisingly, almost every ride at Disney Sea requires the user to be able to transfer. For this specific ride, they don't have vehicles without the chairs bolted to the ground (or the ones that swivel with the door) is what i'm saying.
(pages 28-29: must be able to walk and transfer unassisted)
EDIT: I looked into WHY this ride requires you to transfer and does not allow wheelchairs: It's because it descends a bit (something i wasn't aware of even on the ride) and that they would require people to climb out of several different sections via ladder (no elevator). Someone who cannot transfer from a chair on their own would be denied boarding because they wouldn't be able to evacuate the ride in an emergency situation.