Adjusted age confusion..

So I know at 6-8 weeks your baby goes through a growth spurt and may cry/eat more ect.. Well this what my 6 week old preemie is doing right now. Its confusing because his adjusted age is a week old. Is he not going through a growth spurt then? I hate this because he's rolling over, putting up his head, reaching for things.. stuff a week old baby wouldnt be able to do. Does he developmentally have to stay with his "adjusted age"?