Aint nothing wrong with getting engaged. If he was not open to any suggestions other than those that were four years his junior i would venture to say that he wasn’t to helpful. If he was open to all reasonable ages and what worked out happened to be 4 years his junior then how could anyone fault him.
If boys were open to girls of all reasonable ages (relative to them) and shadchanim gave slight preference to to the slightly older girls, we would see a very very significant reduction in the age gap in a very short period of time.