Yes most solutions are using Linux kernel, so what's being measured is indeed the impact of the way the kernel is being configured to achieve container networki

Yes most solutions are using Linux kernel, so what's being measured is indeed the impact of the way the kernel is being configured to achieve container networking. But that doesn't make those design choices, and the tests, meaningful. Calico, for example, contrary to your assumption, uses neither a Linux bridge device nor iptables for packet forwarding. (It does use iptables for policy enforcement, but that's not being tested here.)