This is a little late so I'm not sure if you're still around, but since you're probably referring to
my thread, let me say:
Yes, cabinets provide structural support. However if your trailer is like mine, you can look at the cabinet in question and see that it doesn't even contact the ceiling. There's an inch or so gap between the top of the cabinet and the ceiling.
So no, in this case, I don't believe the bunk bed cabinet provides much, if any structural support in a
Bigfoot.