Literally the entire section 2 of the linked to file discusses exactly what you're interested to know. It details the evolution of the DragonFlyBSD's network stack, which started as the FreeBSD network stack.
I'm more interested in the higher level takeaway. Why should developers use Dragonfly?
Don't get me wrong, I appreciate the ability to peruse the kernel implementation narrative in the first place. As I'm not a kernel developer I'm left wondering what it means.
e.g. better multicore performance?
https://www.dragonflybsd.org/features/
and here: