alt Hacker Newsnano(1) is GPLv3 last time I checked and that imposes more restrictions than most (all?) of the rest of the code in NetBSD. It is not about being "reflexive", it is a violation of the very ethos of the project. Gnu rejecting non-free licenses from their own distributions is not "reflexive", it is simply not in line with what they want to achieve and one should respect that.
Unless they modify it, the GPL really doesn't impact them. AFAIK FSF considers most BSD/MIT style licences to be compatible. It's the other way around where things gets stuck. Unless they need Linux GPU/WIFI/BT drivers to make things work, of course. Then it's fine.