Count me in as another one who hopes that "alternate drop" NEVER becomes common practice here!
I'm a somewhat picky eater, and I hate being at the mercy of "random" situations like this.
I've tried quiche before- my home ec teacher made some mini quiches, and the ones with ham or mushrooms were tasty. But would I want a whole serving? It might be overwhelming, too rich. And that's the meat or mushrooms, that I happen to like. Vegetarian, not so much. And any time you offer me a choice between that and BBQ, the BBQ is going to win, hands down.
Even a more equitable choice- salmon vs BBQ, I'm not going to be happy if I get the salmon. Because I just don't like cooked salmon- I like it in sushi, where its texture and flavor are different. But cooked, it's entirely different.
I guess a good example would be some of the meals my family has had- when we all had BBQ chicken, that was fine, as I like BBQ chicken, and we were all eating the same thing, with nothing to compare it to. But sometimes my dad would cook himself a steak or pork chop instead, because he didn't like chicken as much. And all of a sudden, my chicken didn't look as good by comparison- I'd rather have been eating the steak.
I'll also second what somebody said about the power dynamics and swapping meals if you get something you don't like. In theory, it's always easy to say "Just swap with somebody" or "If somebody asks you to swap and you don't wanna, you can say no..no is a complete sentance..bla bla bla"
The reality can be different. Sure, Bob may not get fired outright if he doesn't give up his BBQ plate to his boss. But the boss might still hold a grudge that might cause other problems. A child pressured to give something up for another family member is probably going to get heck for it later if they don't.