you probably hold an antiquated notion of how much transaction costs are on blockchains nowadays. It would do good for you to update your priors on this one - you'd be surprised!
That tweet doesn't appear to explain anything about this at all. I take it the information is in the comments? I'm not able to view those.
i don't click on x links, but i bet one trump coin it talked about offchain without taking into account opening up to double spend.