I was under the impression this was one of the main use of *BSD (lot of networking hardware is based on it). Where did you see it was lagging behind ?

I haven't personally tested, but have seen reports that BSD-based opnSense struggles to push 2.5G on modern low-end hardware (mini-PCs). I find that surprising considering I can fully saturate my 25G link on a Ryzen 5 running Linux. The Ryzen is considerably faster than an N100, but not 10x faster.