The original example used the deprecated collection property feature. The new test case is slightly rewritten but still shows the error with hibernate 5.
Note that when using a normal join, the SQL fails beca hhh-9159.zip use no group by is rendered.

The given example is not JPA spec compliant, since the SIZE function requires a collection_valued_path_expression argument but in this case an alias is given.
Still, even a correct usage results in an exception as the use of the SIZE function breaks as soon as other joins are present because of the missing group by.