My read is that certain teapots destroy some of the beneficial nutrients in green tea

Yeah exactly, it's not just taste. While bitter, catechins are the antioxidants that give green tea its cancer-fighting power. So your tea may taste less bitter, but you're getting less benefit. Generally though if your green tea is too bitter you should reduce heat.

I suppose it’s a mechanism by which tea might taste different depending on the cup. Which is by itself interesting