As we all know that some RV parks do not have level parking spots therefore it puts a twist on the body of the coach. I have seen it so bad in South Carolina that support brackets that support the front and rear end caps have broken off from the fiberglass. I also saw an American Tradition in Batesville, Indiana where the twisting of the superstructure popped the windshield off the corner and cracked.
Putting a twist on the superstructure will crack the fiberglass in the stress area's.
Tiffen might recommend it, but they could be wrong also and maybe that is why they are having problems with cracks on the curve part where the roof and the side walls meet.
If you level the coach first so that there will be no twisting stress on the frame of the coach, the slide should come right out. Makes sense if you stop and think about it.