I completely agree with you on the topic. The 6a2 is an odd one. Looks more like a 6b than than a 6a to me. The portrait seems to match more with 6b. I think the main characteristics for it, is the straight sided lettering. Neither the 6a1 or 6b has this. I have a small collection of class 6. One being 6a1. The rest are all 6b. But are all different dies. All very different.