The claim _sd_alg indicates the hash algorithm used by the Issuer to generate the digests as described in Section 5.2. When used, this claim MUST appear at the top level of the SD-JWT payload. It MUST NOT be used in any object nested within the payload. If the _sd_alg claim is not present at the top level, a default value of sha-256 MUST be used.
Currently SdJwtVerifier.hashingAlgorithmClaim(Claims) fails and does not default to sha-256 as specified in the spec.
Quoting the spec (section 5.1.1. Hash Function Claim):
Currently
SdJwtVerifier.hashingAlgorithmClaim(Claims)
fails and does not default tosha-256
as specified in the spec.