2025 is the date that they will complete their demonstration system and show net energy gain. But it will not be a fully functional power plant. Their slightly larger successor system will do that.
But you’d have to listen to their lectures to really understand. The tokamak is a well understood system. They are just using more powerful magnets than ever before, and they recently proved their magnets work. They published their physics basis research paper in Nature, and these are academics from MIT who have talked very openly about their system design. It doesn’t sound like there are any big unknowns remaining except the engineering design of the system itself which is well underway.
Maybe building this tokamak will be harder for some reason. But it really sounds like they can make it happen.