Why it works with version < 4.3 is because of https://hibernate.atlassian.net/browse/HHH-8637. In fact the query in these versions is not correct too because it does not add a restriction to the Dog class implementations.

I started a PR : https://github.com/hibernate/hibernate-orm/pull/1254. It is not completed yet because I need advice from someone that is more experienced with Hibernate than me...