Robosats is not completely decentralized (it's federated) but at least different federations share the same order book, although the order marker needs to decide a priori which Federation will "host" and arbitrage the order.

I didn't know that bisq/haveno had this issue. I also don't know how arbitraging will work for Haveno. Bisq used timelocked multisig, but there's no such thing for Monero...