OGSF is in BAMM, in upcoming AM 6.0, and probably other subs as well, it's like a backbone which is meant to serve a higher purpose. I would leave it for others, more experienced ones, to answer your question, but I see it as the other way around, OGSF as an additional perk instead of OAAFM. OAAFM is meant to serve "Overcoming Approach Anxiety" as the PRIMARY GOAL, whereas, OGSF is meant to serve "Overcoming Guilt, Shame and Fear" as the PRIMARY GOAL. And that's why I think OGSF as an extra in OAAFM, because of what they are meant to do - PRIMARILY.
However, you can't go wrong with either of them.
However, you can't go wrong with either of them.