Most compositors know that the first thing they should do to a shot is de-grain it. They also know that they have to add back grain at the end before delivery. A shot delivered without grain is unacceptable work. And it needs to match what was given.
As a result, there are a myriad of grain management tools out there. In my experience however, they’re often used completely incorrectly.
A good VFX supervisor has a particular kind of check that they do. It drives compositors crazy. Especially the ones that don’t know how to handle grain well.