It's complicated but I think they said the transactions will happen off - chain, with Bitcoin being used for deposits and withdrawals.
No shit, but it would have to be far more complicated than that. After all, the Lightning Network isn't being used by any major wallets yet, so what solution could Kim Dotcom have that's better than everyone else's?
It seems like he's riding on his reputation to avoid giving enough details or insight into his project.
It's certainly a very interesting concept, but he got in partway through this ICO bubble, which really doesn't give me a lot of confidence. He could very easily put out a sub-par project without breaking any outright promises that he's made, and make off with millions.