I generally agree with the only order what you can eat, but we have dietary needs that mean we order food the night before and while something may sound good on the menu, sometimes it is so bad it isn' good, so there are times we order multiple items because we aren' sure if one will be good or not and don't want to end up not getting something edible for us.
So I say don't judge, you don' know what that person's situation is, they may have ordered something and found it disgusting, so they ordered something else. They may have a situation like mine, there may be other circumstances that led to it, who knows.
Luckily with Disney most food doesn' go to waste, it gets recycled into compost, animal feed, etc. whenever possible, so you can take a little comfort in that much at least.