Oh sure! I have done both the rule of thumb is not to cut back more than one third of the plant at a time. I cut mine back big time early in the spring because they were growing over my roses "space". Roses don't like that you know. They want full sun around the root to prevent rot. I might have to transplant the phlox this fall.
I have another ground cover I am cutting back to a nub today. They are going to seed. It is ruellia. It was sent to me as seed five years ago, and I have just been dividing it into clumps in my rocks. Hope you don't mind a pic, they did good this year.