The Rule of So is a commonly used description of a all to typical fallacy whereby one strawmans a post with an off topic rant, such as here.
In this case the topic is God's purpose.
Paul said, "God is the one who, for his good purpose, works in you both to desire and to work"
So, are you arguing that an off-topic post is a strawman, or that a strawman post is off-topic?
Sorry- I had to do it. Do I win the Trifecta?
But it is a real question. I can see that there can be an overlap, but I don't see how one is logically an inherent part of or linked to the other.