Yes, they have to post all the warnings to cover any issues that may come up.
Our old trailer was short and rode about 4" high up front. Yes, we were one of 'those' people you see on the road. Frequently I'd not unhook for the night and we'd sleep that way. Yep, like being on a big recliner
As someone else noted, the refer can be out of level by quite a bit and still work just fine.
I got the trailer on a level pad (checked with 4ft levels) and then leveled the trailer. I checked inside several places on the floor and refer. Another check I do is door frames. Check to make sure the door is still centered in the frame. If you have a couple of doors that makes a better check than levels in many cases. Also check to see of the doors will stay in one place. Open 45 deg. If they start to open more or close then the frame isn't level.
As far as comfort, my 'picky' place is the shower floor. If it is tilted back too far the water won't drain.
charlie