Ah, but I think the decent early years are a necessary but not sufficient component of why I'm capable of being casually indifferent to bonding. The personality/genetics/epigenetics are why I ended up casually indifferent given the decent early years (whereas most people with decent early years don't), but in an AU without the decent early years, I don't at all have the confidence I end up like this.

What I got out my early childhood was the idea that I don't need to please other people (and that saved me when I got a bit older and my parents started signalling that they weren't pleased with me). Fritz did not get that message in his early childhood, not from either of his parents.

I have a more well-thought-out rationale, but it's late and I have a long backlog of comments to work through. ;)