I guess you can call that hashrate escrow... But a merge mined sidechain with BitVM bridge is very much a hashrate escrow already. The difference here is that if you don't want faster blocks than Rootstock, you don't create Sidechains and worry about the consequences of that, instead you just accept transactions as they come without any computations, and update the state later... Separating DA from Compute. The obvious upside is synchronicity which makes the entire system safer and easier to reason about. Things all happen at the same time including their side effects in parallel contexts, and as long as majority of miners are honest (or ZK verifier is valid) you reach the same conclusion globally as you calculated locally.