You're thinking of the POSIX personality of Windows NT of old. This was based on Interix and has been deprecated about two decades ago and is now buried so deep that it couldn't be revived.
The new WSL1 uses kernel call translation, like Wine in reverse and WSL2 runs a full blown Linux kernel in a Hyper-V VM. To my knowledge neither of these share anything with the aforementioned POSIX subsystem.
The new WSL1 uses kernel call translation, like Wine in reverse and WSL2 runs a full blown Linux kernel in a Hyper-V VM. To my knowledge neither of these share anything with the aforementioned POSIX subsystem.