According to https://d0.awsstatic.com/whitepapers/compliance/AWS_HIPAA_Co... page 12 the PostreSQL flavor is HIPAA eligible now:

> Customers may use either the MySQL-compatible edition of Amazon Aurora or the PostgreSQL-compatible version as part of our BAA.

But according to https://aws.amazon.com/compliance/hipaa-eligible-services-re... only the MySQL flavor is:

> Amazon Aurora [MySQL]

I assume the latter simply hasn't been updated yet.