There are some recipes that call for a certain volume of flour, some
that say to sift it. Others call for a volume of sifted flour, which
means sifting it first. The latter is probably more likely to result in
a more exact replication of the author's ingredients. Others go by weight.
I am a lot more careful with measuring for baking recipes than other
things, but sometimes things just aren't the same. Temperature and
humidity can cause subtle and no so subtle difference. When I used to
make chocolate chip cookies on a regular basis I could tell by the
consistency of the batter if they were going to be especially good and
could add a little more flour. The same goes for pie. Sometimes the
dough just isn't right and you have to use extra bench flour and roll it
in to get it just right. Bread makers develop a feel for the dough and
adjust.
It seems to be something of a science, but not an exact science.