Not sure about the concerns op mentioned, but cooking fatty things in it is basically adding oil/seasoning. Cooking acidic food eats away at the coating, if only slightly, so you will need to season it intentionally more often.

Technically, if you only cooked tomatoes and other acidic food in it it will remove the seasoning over time if you don’t do anything. Guessing they are saying that eventually you will end up with more iron in your food than you should have.