I think he’s suggesting bip-300 implementation would be attack on eth and Monero.
Because you could have privacy sidechain and sidechain for Turing complete smart contracts using drivechain bip.
Discussion
Interessting thought. Maybe.
https://medium.com/coinmonks/bitcoin-sidechains-bip300-cd30369ce3c4
Fiat jaf is a big drivechain advocate. I message him sometimes on drivechain telegram group.