GIMSO is defined as memory safety without caveats. The only way to get it (currently) in C/C++ is to compile with Fil-C.

You have a good point otherwise, but Go is considered memory safe anyway. And it probably makes sense that it is, since the chances of exploitation due to memory safety issues caused by races in Go are infinitesimal. It’s not at all fair to compare to the exploited-all-the-time issues of C/C++ (when you make the mistake of compiling with something other than Fil-C)