Read Band of Brothers. You’ll see the high rate of attrition and how the new guys were looked at.
I wouldn’t use “Band of Brothers” as an example, because the airborne divisions WERE pulled back to England for a period before they were committed to Operation Market Garden (the jump on Holland). I think Frank is referring to other division size units which stayed at or near the front while drawing replacements from the rear area manpower pools.
In VN, in my experience, FNG’s were were considered liabilities until they got some experience, the stupidity factor. After the first couple of months, New Guy’s, were rated on ability.