Q: Just Desserts rules remind us that order might matter when discarding multiple Guests, but we can’t see any situation where one would ever discard more than one at a time.

…Does this mean players might be allowed to rearrange the discard pile under some circumstances?

A: Sorry for the confusion on this; it’s the downside of attempting to cover all cases. In actual play, the only time you have to discard more than one guest is on the first turn, and then only if you get multiple matches on that first draw. It’s pretty rare but it can happen, which is why the rule was written broadly. Players can look through the discard pile, but never rearrange it.