As the author of a CMD replacement long ago, I remember Rex Conn's comments on how the command-line parser of COMMAND (and hence CMD) was quite arbitrary.

What was implemented, though, was a set of characters that acted as separators between the command name and the rest of the command tail. To many people's surprise in years gone by, this included not just whitespace but things like forward slashes and equals signs and commas. If memory serves, there was even an undocumented NLSFUNC table for looking them up, although my memory might be mis-serving me here.

So one could, for example, treat the COMMAND command line as if it were CONFIG.SYS and do SOMETHING=ARGUMENTS, which was particularly useful for the built-in PATH and DPATH commands.

MS/PC/DR-DOS, and indeed OS/2, programs were passed not a set of arguments but a single command tail, limited to 126 characters on MS/PC/DR-DOS and limited to 64KiB for the whole command-tail(s)-plus-environment-strings on OS/2. (It was the runtime libraries of programs written in programming languages such as C that did of all of the fakery that pretended that there was an argv[], and notably there were slight disagreements between Microsoft, Borland, and Watcom on the wild edge cases.) Usually, the first character of this command tail was the whitespace separator character that got entered by the user. But it didn't have to be.