I mean in terms of privacy, in comparison, it’s basically strictly better? It switches who learns the list of client IPs, but now matching that to plaintext traffic takes two entities working together instead of just one of them.
Discussion
Just noticed it's using Wireguard on top of QUICK, so even if QUICK was broken you'd still effectively have a Wireguard connection to Mullvad. So then indeed it should be strictly better. I initially assumed they used something else to get to Obscure and Wireguard only for the second hop.