I'm having a bit of trouble understanding your point. Perhaps you could give a specific example of what you mean by "ever-more-aggressive flows?"
> This effect didn't happen with in the TCP world, since most applications don't run with enough privileges to speak TCP without the kernel's involvement.
The argument is that while kernel developers wouldn't start this supposed "arms race", but application developers would.
I think we would have seen this already with things like (m)uTP if it was an issue.
(But even then, just open lots of TCP connections if you want to have your unfair share of bandwidth)