I thought I read someplace, and had believed, that the 30-50ma GF detection inside of an AFCI was to some point a "CYA move" early on.
I examined a QO115CAFCI a couple years back in an attempt to understand enough about the inner workings to be able to discuss their merits and pitfalls with a little deeper level of understanding.
It is much easier to detect a parallel arc since its current level is so high compared to "normal" loads (except inrush, noise etc).
A series arc is harder to discriminate since the current level is well within the "normal" load region.
I think the GF detection may have helped makeup for a lack of a true ability to reliably detect a series arc. Understanding that some manufacturers may be better at it than others.
If I had the spare time I would like to examine the new GE unit without GF detection.
... Never mind, spent way too much time at this last time