You get the same properties from a merge mined sidechain, but miners don't have to cooperate. Also, by using a homomorphic commitment scheme, less burden is placed on the Bitcoin chain and attestations have greater privacy and censorship resistance.
Ah ok, that makes sense - merged mining without the need for Bitcoin miners to actively cooperate is indeed an advantage (even if it is not a big burden for miners to do merged mining in practice). Thanks for pointing this out!