I have no idea how unusual it is to use liquid cooling in other power supplies. Water has some great and unusual properties, so I am sure that using it in some power supply settings might be in order. Heck, some folks are using it in the cooling solutions for their desk top computers.
It was a failed attempt on my part to support the idea that sometimes a quantitative approach with TOTAL cooling needs is in order.
We did find several other methods of cooling when the actual supply was opened, but none too unusual for the size being considered...or so others tell me.