Apparently, both ways of doing it exist:

To make chunky peanut butter, peanut pieces approximately the size of one-eighth of a kernel are mixed with regular peanut butter, or incomplete grinding is used by removing a rib from the grinder.

https://www.madehow.com/Volume-1/Peanut-Butter.html

Personally, I figured, it could be bad when you don’t grind them fully, because you might end up with very large peanut chunks still left, but I guess, that’s kind of answered just before the previous quote:

Peanut butter is usually made by two grinding operations. The first reduces the nuts to a medium grind and the second to a fine, smooth texture.

So, I guess, you just do an incomplete grind for the second grind…