AFAIKS, the fix for this was mostly reverted by HHH-12470 Closed . Should this ticket be reopened or a new created?

From my understanding, the revert of line 77 in StatementPreparerImpl.java, forcing the batch to execute, causes inserts of joined tables to no longer be batchable. The revertion of tests in HHH-12470 Closed is also evidence of this I guess.