Yup, that’s about where I was.
I agree.
Usually, leftover food, if it‘s on a plate - not in a Tupper box and/or in the fridge- is supposed to be there for the taking by any comer. This is also what another participant in this debate has already pointed out.
That‘s the way it‘s supposed to be (in my country at least, don’t know about British customs in this regard), and the custom I was raised with😊