IBM i (aka OS400) has three types of updates :

• PTF - fixes a specific bug
• PTF Group - fixes an OS feature (DB2, Java, Apache...) or add improvements (Full LIMIT and OFFSET support, ...)
• Cumulative packages - fixes the most important bugs and security vulnerabilities

Generaly the big features are available with a major OS version (V7R1, V7R2...) and are backported to the previous supported releases with a new level of PTF Group.

LIMIT and OFFSET has landed in V7R3 *BASE but the full support including subqueries has been distributed in PTF Group.

Hibernate discovers the dialect to use with the version of OS which doesn't include the DB2 PTF Group level. I think is dangerous to create a dialect using a feature which is not present in the base of OS release because it will doesn't work if the PTF Group isn't installed. It will be hard to a novice to understand why hibernate doesn't work without extra configurations.