I dunno, Rob - is my answer to that.
As you allude to, they are "Official NSRA 6yrd Targets" (Air 7 and Air 8 on the NSRA shop website).
Are they easier? I'm not sure, although I'm sure I've read that some folks have found the opposite!?
Bob (Zooma) may be able to answer, as he runs the excellent MPL 6 yard postal comps' on here.