A very thorough analysis but I am pretty sure the only possible answer is the lack of practise. I haven’t written in cursive since it was no longer required in the 3rd grade if I remember correctly.

I learned to speak and walk and all that quite early, and my parents did not change my hands. And what comes to Aspergers or Autism, I’m sure I’m somewhere on the spectrum. But I don’t think it’s good to try and find issues where there really isn’t any, people have different traits and that is that.