well from what I have observed and again my opinion is meaningless but there seem to be cases where only the upper is affected
ex:
and others where the mid-face also grows vertically along with the upper jaw
^ or maybe that girl just has a naturally long upper lip and a really low mouth (vs her eyes)... who knows?
hmm hard to tell cause one's smiling and one's relaxed but I get your point.
surgeons only care about LFS when it comes to the jaw and it's relation to the soft tissue, which is basically the barometer for normal growth, so gummy smile or lip incompetence would be the measurement of how much to correct. As far as the whole face growing wrong and throwing everything off, definitely possible I guess. I think everyone experiences vertical growth to some degree, generally the less the better which is why models faces are often so close to perfect forward growth (and so rare). it's only the extreme outliers that we notice and label as LFS