I'm not actually sure what the proposal here is. Are we suggesting that all Python's means of terminating a process should use the same exit code?

Note that doing so would be a backward compatibility break, as os.kill() is documented as having the behaviour seen here (it's just that SIGTERM isn't a particularly meaningful value to use on Windows). subprocess terminate() doesn't document the exit code sent on Windows, and maybe should - but 1 seems a reasonable value (it's the C EXIT_FAILURE code after all). I don't fully understand the issue multiprocessing is trying to solve, but it seems to be around signals, which are very different between Windows and Unix anyway.

So, in summary - I'd need to see a specific proposal, but my instinct is that this is only an issue if you're trying to cover over the differences between Unix and Windows, and this isn't a case where I think that's advisable (the current situation is "good enough" if you don't care, and if you do, you have the means to do it right, you just need to cater for the platform differences yourself, in a way that suits your application.).