Since Vlad commented on Twitter that the issue isn't clear yet, let me try to clarify.

I created a reproducer here: https://github.com/schauder/issue-HHH-12999-superfluous-join

The issue is: Given two entities with a one-to-one relationship (Parent, Child) querying a projection containing a field from Parent plus the referenced Child, Hibernate creates an inner join.

This excludes all values from the results where the reference to the child is null.