Can I have hair transplant 2-4 week after forehead type 3?

as I know you can't do forehead type 3 surgery and then do the hair transplant after a month (temples and crown) but some doctor told me i can have it after 3 mont and some others told i can have ht after 2 week so iam confused now and i want to know why i must wait 3 or 6 month and what could happend if i dont waith that much