|Not that strange; it was based on the SysV command of the same name. |
My memory's fuzzy, but I remember the version included with NT4 resource kit only allowed dashes.
When they added it to Windows, they must have added slash support to bring it in line with Window's standards.
Then in Vista, they rewrote the help text and now they recommend slashes. From Win7:
Usage: shutdown [/i | /l | /s | /r | /g | /a | /p | /h | /e] [/f]
[/m \\computer][/t xxx][/d [p|u:]xx:yy [/c "comment"]]With Win8+, Microsoft pushes the PowerShell command Stop-Computer.
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