Use More Force
That's essentially what this boiled down to. I was correct that this is a self-extracting crank and I was performing the steps that should have worked. More force was required.
@JoeK and @Carel were both correct. @JoeK was right that there was indeed a very loud and obvious "snap" when it finally loosened, and @Carel was right in ...
There will be some corrosion and probably loctite on the bolt. It will go (loosen) with a snap, so don't hurt yourself.
You can either use a bigger tool (more leverage) making sure you have a good deep fit in the 8mm and someone to hold the bike steady
or warm the area up with a blow torch first at the risk of damaging surface finishes and plastic parts.