I'm kind of in the middle, mainly because I think this is a know your audience type thing. And it isn't just about Reba and how close she is to the couple, or even the fact that it was casual. I can picture myself hosting casual events where it wouldn't even land on my radar and I can picture myself in other events finding it rather offputting.
On the latter, picking up on something Toots said, if I had planned a separate serving of dessert on the terrace, with after dinner drinks and coffee, this would really annoy me. Not only might others decide they want dessert sooner, it also means I drop what I'm doing and either serve it up or package it. At other events, if someone had to leave early, it could be *me* offering the dessert.