Our first trip was a duffel per person, second trip was per family......
As for the suitcases, I think they are referring to 1 checked per person. We checked more and *way* more when we left and there was never even an eye blicked.... I guess if everyone on your trip checked extras, then maybe the size bus they use to transport between locations might not work as planned?? But, I'm guessing they always know that there are *some* of us in every group....... LOL!