He does the math to prove that when you subtract all the mandatory protocol and frame headers you end up with practical maximum of 949.28 Mbps on 1 Gbps line. Providing charts with 1011 Mbps in favor of WireGuard makes all the comparison at least dubious. Another thing he mentioned is the test compares ChaCha20 cipher with AES256-GCM which is totally unfair.
Why would you invest so much in perfect code then to fake the benchmarks?