Earlier quoted context omitted.
I have been developing using the bash shell on Windows. It's got a couple quirks (like a couple second startup time on first startup, or docker issues) but it has performed exceptionally otherwise. I've primarily been doing nodejs development and installing random unix packages I need.
Out of curiosity have you thought about just running a linux server in a VM and sshing into it from the shell? It seems bizarre I know, but you get a "real" linux then, while still keeping a major OS for software compatibility with user apps.
If 'real linux' is the Linux userspace, then that's what you're getting with Ubuntu - all of 'Linux' except the Linux kernel. WSL allows the NT kernel to handle all of the Linux syscalls. If you consider just the public interface, then WSL is also 'real linux'.
Of course this is all theoretical because there are still some bugs here and there. Those are being dealt with and WSL is making great progress.