The answer to that is yes and no. If you go to most hardware stores and want to buy an M6 bolt, it would more than likely be 1mm pitch (thread pattern). That’s kind of the standard size.
But there are other pitches available. For example, McMaster-Carr offers M6 in .75 and 1mm. And I believe there is another pitch as well, but I can’t remember the application it is used for.
I always like to include pitch when suggesting a nut or bolt, just in case the person running to the hardware store doesn’t grab the wrong pitch if that store offers multiple pitch sizes.
Pitch is more critical when buying American sized bolts. I’m sure everyone is familiar with the term fine thread and course thread bolts. It’s just another name for different pitches.