This should be fixed in 5.1. Please give it a try.

Previously we tried to keep the JPA schema generation as plain as possible in regards to the spec. In 5.1 I did a lot of work to marry the features JPA schema generation and Hibernate's more mature and broader HBM2DDL tooling. In other words, running JPA schema generation should now understand the various (non-conflicting) HBM2DDL options as well