It is a British website and a casserole is covered.
Just double checked and it says that it should be covered, probably to help in these cases
I've had this before though.
I think I'm making a stew style meal and get lovely, well cooked and seasoned meat but no gravy. I can't pour flavoured water over mashipots. Or I can't expect the 'rents to enjoy it anyway.
It's probably a class thing. Like Gazpacho soup.