The pfsense kernel implementation was done while ignoring the feedback of the wireguard project creator, Jason Donenfeld. When it shipped I believe the Donenfeld had to call them out because the implementation had issues and it had been merged into the FreeBSD kernel.

This is a starting point to learn about this particular drama:

https://www.reddit.com/r/PFSENSE/comments/m7vi3b/wireguard_r...