rock falling off the wall is only part of the deal. As I said, attaching the rock to the studs properly is part of the structural integrity of the building itself. Without sheetrock, the framing has very little strength to resist racking. With the rock, it becomes much stronger. A poor attachment method will not allow the wall system to perform as it is intended. Wind loads are not handled as well as there is effectively no bracing to the outer walls due to the poor build practices of the inner walls which will cause more flexation to the entire structure which causes premature failure of the entire system.
A house is not a wall and a roof and a floor, it is a complex engineered structure where each structural unit in the building provides strength to the total structure. Remove one and the entire structure is compromised.
and just because there is no inspection does not mean you should do work of lesser quality that what is required in areas where there are inspections. A quality installer installs quality, regardless who is looking at it.
and warranty is the last thing I worry about. They are simply covering their rears. IRC is designed so the building meets engineering requirements. That is what is going to make the building sound, not some warranty from a manufacturer of a product.