Top level checks are only used for miniscript APIs and not descriptor APIs.

[sanket1729]

    #[test]
    fn test_2() {
        let desc = Descriptor::<String>::from_str("wsh(thresh(1,pk(A),s:pk(B)))").unwrap();
        let desc = Descriptor::<String>::from_str("wsh(thresh(1,pk(A),s:pk(A)))").unwrap(); // This should also ERR because duplicate keys.
        
        // But miniscript APIs are fine.
        let ms = Miniscript::<String, Segwitv0>::from_str("thresh(1,pk(A),s:pk(B))").unwrap();
        let ms = Miniscript::<String, Segwitv0>::from_str("thresh(1,pk(A),s:pk(A))").expect_err("This is not a valid miniscript");
    }

brunoerg/bitcoinfuzz#73 (comment)

We should have those in descriptor APIs too. In the above example, we have duplicate keys being allowed in descriptors.

[apoelstra]

I plan to address this in 2025 by overhauling our sanity check system.