Sorry for all the messages. I have found out that it was not the applyIncrementSizeToSourceValues returning false that was the answer. It was the change from using ‘none’ to using an explicit classname.
So, using the existing NoopOptimizer works, provided you set the hibernate property to this:
hibernate.id.optimizer.pooled.preferred=org.hibernate.id.enhanced.NoopOptimizer
instead of ‘none’.