Hmm… That makes sense. Though if you are building from source, the only gain you have over regular go tooling is downloading from your favorite mirror rather than github&co. I hope it doesn’t install these source-packages for prebuilt binaries…
I believe they don't allow internet access during the build (so everything needs to be vendored, or things stuck into GOPATH); those packages are probably for the second option.
My impression is that OpenSUSE go packaging is a bit behind though. But I'm not an active packager so this may have been fixed.