Don't know if this is definitive, but: https://www.johndcook.com/powershell.html#:~:text=The%20core%20of%20the%20PowerShell,1003.2%20standard%20for%20Unix%20sh

Don't know if this is definitive, but: https://www.johndcook.com/powershell.html#:~:text=The%20core%20of%20the%20PowerShell,1003.2%20standard%20for%20Unix%20shells. https://www.johndcook.com/powershell.html#:~:text=The%20core... POSIX Korn shell, specifically, according to Wikipedia: https://en.wikipedia.org/wiki/PowerShell#Grammar https://en.wikipedia.org/wiki/PowerShell#Grammar so maybe it inherited 2>&1 from Korn shell, which in turn was POSIX. But yeah, Powershell was not built purely to be a POSIX shell, but I thought it tried to be compatible where it made sense (hence the seeming clash of cultures).