While I do believe that the letter was written as a joke, it sounds like the kind of thing my family would appreciate. We always have the party at the house with the most space, and right now the person whose house that is can be hilariously compulsive about details.
For instance, there is a designated family mashed-potato pan, which my eldest sister happened to receive as a wedding gift in 1960. It's really a Magnalite roaster, but it's large enough to sit across two burners, so it's the only pan big enough to handle the number of potatoes we have to cook. The cooking of the potatoes cannot commence until that sister and her pan arrive, and she is ALWAYS late. Every year until recently, there was always a brouhaha when it came time to peel those potatoes, because the hostess of the moment never seemed to have decent peelers. A few years ago I couldn't make it to dinner, so I went out and bought 8 nice OXO potato peelers, and sent them to that year's hostess in a wooden box. My gift to the whole family was NOT having to listen to the annual argument over what to use to peel the mountain of potatoes! Now the box of peelers is part of the tradition, formally handed over whenever the hostess duties change hands.
I'm guessing that the "non-regulation" casserole pan that someone brought the year before was actually too large to fit in or on the stove, necessiitating tearing the kitchen apart to find the last remaining unused dishes to heat the spuds in (because as we all know, spuds that travel will not stay warm until they reach their destination!)
We do assign specific foods, and we stipulate quantities. Particular people are asked to do particular things because we know that they can be counted upon do do those particular things well. When people trade, bad things tend to happen, like the time my sister "X" insisted on bringing the stuffing, even though she had never made stuffing for 40 people before. It turned out badly, and no one ate it. You can change your assignment, but we ask that you do it early enough to make a trial run on the dish, to be sure that we don't get ugly surprises. Sometimes the orders can make no sense -- when I was in college I was always under orders to bring fruit salad, even though I *hate* fruit salad and do not eat it. There is in fact only one person in the family who likes it -- the husband of the sister who always told me to bring it. I guess that her theory was that since I only had to make a small dish of it, it was cheaper for me, but I still didn't like bringing it. I finally got out of it when one of my nieces got old enough to join the rotation.
My SIL is a rather militant vegetarian; having her at family meals is a trial, because she constantly comments on how "bad for you" all of our favorite foods are. (Which is amusing, actually, because we are not casserole people; there are mountains of identifiable fresh veggies on our menu, though we are generous with the butter.) She is presently miffed because she always brings the same thing to all parties, and no one will eat it -- vegetable soup. What she doesn't see is that their refusal to eat it isn't so much about her cooking (though it's VERY bland), but about the fact that it is soup, and thus very filling. No one wants to fill up on soup and feel too full to eat the holiday-only favorites that they have been anticipating for MONTHS.