When people talk about bypassing the kernel, they mean taking control of TCP/IP (UDP, IPv6, ICMP, whatever) in userland; for instance, doing your own congestion control algorithm, or binding to every port on an address all at once, or doing your own routing --- all things the kernel doesn't expose interfaces for. They usually don't mean you're literally not using the kernel for anything.

There are near-total bypass solutions, in which the bulk of the code is the same as you'd use with this WireGuard bypass, where ultra-high performance is the goal, and you're wiring userland up to get packets directly to and from the card DMA rings. That's a possible thing to do too, but you basically need to build the whole system around what you're doing. The WireGuard thing you can do as an unprivileged user --- that is, you can ship an application to your users that does it, without them having to care.

Long story short: sometimes this is about perf, here though not so much.