Scanning through recent commits && the github repo this is clearly not the case - there are way too many outstanding issues and outright missing support for various things. Is this another project where it was written in a different language or something and then ported out?
Can you clarify?
gVisor is not a rewritten version of an internal tool. The code you see really does run in production for App Engine and Cloud Run. While there are some internal modifications to better integrate with internal infrastructure, the vast majority of the code is identical to open source, critically including all of the system call handling, filesystem, and memory management code.
While browsing through our issues will show that we still have plenty to work on, the vast majority of applications work well inside gVisor.
As a bystander from outside, I generally don't like VM type of mechanism as security mechanism. Unless it's actually a VM hypervisor. That way hardware can be utilized to define a relatively simper and more robust security model. (Of cuz, not saying hardware is always superior please don't chase me on this direction).
On the contrary, true software sandbox like ebpf and webassembly with limited capabilities in its building blocks and clearly defined application scenarios, are better ways to do security in software.