No, that's really not at all what gVisor is. gVisor is best thought of as user-mode Linux --- a complete reimplementation of most of the OS kernel. It's not a system call filter; it's something much closer to a VM than to seccomp.

gVisor is a very cool codebase. As an illustration of the approach: it includes its own TCP/IP stack; we use it in our command-line dev tool to allow people to SSH to their VMs over WireGuard without having to install WireGuard or obtain privileges to manage WireGuard.

gVisor, for better or for worse, does a whole lot of other things than just seccomp filtering, and it shows in performance tests.

gVisor does more than filtering, they basically reimplemented the syscalls in an application kernel. At least with seccomp the performance overhead is minimal.