dash is only allowed in the middle. labels can't start or stop with it. so it wouldn't affect the command arguments.

    The labels must follow the rules for ARPANET host names.  They must
    start with a letter, end with a letter or digit, and have as interior
    characters only letters, digits, and hyphen.  There are also some
    restrictions on the length.  Labels must be 63 characters or less.

https://www.ietf.org/rfc/rfc1035.txt

it's more likely that in the late 90s they just made up their own argument parsing that they liked and the application has just used that ever since.