I like to use a restaurant reference. We went out to dinner a few years ago, and my uncle's meal was the last to come out, 45min later than everyone else's. If you work in actual restaurants, you know this is ****ing unacceptable because the diner has to watch others eat, and then everyone has to wait for them. He speaks to the hot shot manager and takes a firm stance. The manager starts giving excuses as to why it happened and tried to play it off like it was no big deal. My uncle used no profanity, but made the point very clear that that was piss poor service to be ashamed of. He demanded his portion to be free, and he got it. A $30 rib slab along with drinks.
At least your uncle waited for the manager to respond (poorly so, I agree that that situation is unacceptable in a restaurant) before demanding a free meal.
Anyways, I think a good manager in a decent restaurant should have offered to comp all or at least part of his meal.