I don't understand the technical aspects and I'm not an expert in law but I know that the moment he talks about stablecoins he's referring to a currency pegged to the US dollar in that sense how the hell can he talk about decentralized when everyone knows well that it's pegged to the US dollar...
Currently, the dollar acts as a measure of the value of the cryptocurrency, as well as in the real world. In this case, it would be logical for bitcoin, not the dollar, to act as such a measure of value in the cryptocurrency market. But this will become possible only when BTC ceases to be so volatile.