maybe we are just speaking about the same thing differently
my units will be plumb and level but my trim may or may not
i will run my siding level but will adjust my trim to help visualy make the windows appear level,frieze boards slightly tapered,soffit hung to more equal reveals all can be used to achieve this
and many times settlement is not the issue,walls are built wacky new windows in new construction installed out of level,i don't think running my stuff out of level is the right way to address these problems