Sorry, I don't understand what you are trying to say here. Tangzhong doesn't just "pack more moisture into a dough while keeping it easy to handle". It changes

Sorry, I don't understand what you are trying to say here. Tangzhong doesn't just "pack more moisture into a dough while keeping it easy to handle". It changes the loaf after baking, too. From what I understand this is because the flour that is cooked in the roux has its gluten destroyed, thus you have a paste in your dough that isn't imparting structure in the same way and holds moisture in a different way, even after baking. So tangzhong can give you a higher hydration, but it's not necessarily the same thing as your 80-ish% hydration dough.