Jenny0329, whether it is a legal diagnosis, or not doesn't really matter - complex trauma exists and there are many mental health professionals, who work with trauma who believe in Complex PTSD when the trauma is complex and severe.
I think mental health professionals identifying complex trauma and understanding this requires specialized trauma counselling, as well as understanding the PTSD symptoms are often more severe and harder to treat both medically and with therapy, is good and very necessary.
There are lots of terms banded about that aren't legally corrent - like 'Lifelong PTSD'. As far as I'm aware there isn't a legal diagnostic criterion for that either, but some mental health professionals and sufferers use that also.
I was told I had Complex PTSD, then discussed this with my mental health doc and was told 'legally' I have Severe PTSD with Delayed Onset & Major Depressive Disorder and these were the terms used in my documents submitted for a disabaility claim.