Well, there you go. It just shows that everyone is different. When I'm diving, no matter if the water temp is 84+ degrees, I wear my full 3 mm suit. I don't get overheated in the water and if warm up on the surface, I can pull the top down. I've found that over multiple dives on multiple days, I'm glad to have it.
When diving in cooler water temps, like those around Belizean waters in the winter months, I've even been known to wear a light hood, neoprene beanie cap or a bandana, to help keep my head warm too.
The padding I have before I even donn my wetsuit doesn't seem to help keep me warm at all. It's more like there is more surface area to chill.