Hi y'all.
Let me see if I can help explain how wool is exothermic.
The molecular structure of the interior of the wool fiber has the capabiltiy to accept water molecules into it. This process allows the molecular structure to become more stable, releasing heat as a by-product.
This means when dry wool gets wet, it releases some heat. If you happen to be wearing the wool, this helps keep you warm.
This phenomenon works in normal wool clothing to help regulate your temperature.
As you get hot, your "heat" is causes the wool to release the captured water molecules, using the heat you supplied as fuel. The heat is "absorbed" by the wool and you feel cooler.
When you get cold, the wool incorporates the water back into its molecular structure, releasing heat to keep you warm.
Personally, I think that the effect is minimal in a wetsuit. It is a true claim, but the impact may not be measurable in this instance.
However, if you want to stay warm and toasty topside, wear wool. Because it has the ability to regulate temperature you don't have to change your layers to compensate for temperature changes. With synthetics I'm always changing layers to stay the tight temperature. With wool, I wear the same sweater all day long.
Cheers.
PS - My qualifications are a Bachelor's degree in Biology and I teach wilderness survival courses covering this exact subject.