It is common to define engineering as applied science. A more accurate idea is to recognize that science is about ideas and theories. Engineering uses science to build or create things: computer programs, bridges, machines, etc. Any kind of artifact.
Aside from science are what I call established practice. This is where you find engineering standards. You find these in building codes, manufacturer specifications, etc. Various trade associations publish what are defacto accepted engineering practices: the Southern Pine Association, the American Institute of Timber Construction, the American Institue American Institute of Steel Construction. and the American Concrete Institute.
Engineering standards regarding slab-on-ground foundations address how they are to be designed and constructed. What they do not address is how they are expected to perform.
Let me repeat that:
The applicable building codes address how foundations on expansive soils are to be designed. They do not address how such foundations are expected to perform beyond what should be obvious: foundations on expansive shall be designed to resist bending that will cause the frame structure to be damaged so that the frame structure can no longer carry design loads.
Note what should be obvious: structural damage is a really bad thing and should be addressed, but there is no mention of distress as opposed to structural damage. There is nothing in the applicable codes that implies proper design or construction will eliminate what I call normal when the house is founded on expansive soils: minor drywall cracking. minor cracking in the brick veneer, cracks in the finish floor, and sloping in the finish floor.