I think I know what you may have in mind when you describe the "interpersonal dynamics" of a "would-be middle manager", and I probably agree with you (original author here).

But some of the best "people" people that I've seen in my career have been the most technical, also. They were really good at being able to communicate the value of their solution, the problems it solves, and risks and rewards. They could get buy-in from stakeholders and other teams. They could listen empathetically when faced with issues and blockers. And they did so with authenticity and genuine care because they were passionate about software engineering.

I believe those are skills that can be learned and practiced and that you don't have to be necessarily "social" to grow in that area.