This very is interesting. Science Diet´s main marketing strategy is to
scare people about the level of phosphorus in other foods because the
cat may be in the early stages of kidney disease and this "excess
phosphorus," according to them, will add to kidney damage.

It's not a marketing strategy, it's science and research--something you
apparently don't know anything about.

So how come
is it ok to feed S/D if S/D should not be fed to a cat with kidney
problems?

s/d should NOT be fed to healthy cats that don't have any urinary problems.
Period. Don't go trying to put words in people's mouths....