Oh, huh, suddenly I have no idea if it's canon or not. The dinner with ZYL and SW is in a restaurant, and even if he's flatting, going home for the Reunion Festival would be very normal... Do we see any more of Changcheng's homelife than that? I've just been assuming (and may have been incepted by fic).

but if they don't even know enough about his work, they may not be all that interested in what he's eating?

Maybe. Or maybe they talk about other things at family dinner, and Changcheng doesn't mention the SID because someone impressed on him how secret the work there is (and also he's a bit embarrassed about his klutziness) (and also, when dangerous things happen, he doesn't want them to worry)?

But I'm equally in favor of both headcanons - this one, and the opposite one where he eats great nutricious meals at home and is horrified to see how much it's not the case at work. :D

Aww, yes. Or option c), he imprints so hard on the SID that everything they do it good and right, even when it's objectively scurvy-inducing. :D :D :D