"Dot pitch," when used as a term of art¹ related to CRT monitors, is the pitch of (i.e., distance between) the holes in the shadow mask. It has no relation to the pixels as displayed by the computer's graphics system (or the resolution of any other video source).
Think of it as a grid of dots overlaid on top of the pixels generated by the computer. If you look closely, you can easily see that pixels may span several holes in the mask, and some holes may be partially illuminated due to being near the edge of a pixel. Here is a close-up of an image on a CRT with the pixels² showing "through" the holes in the shadow mask:
(Image: Selçuk Oral, WikiMedia Commons.)
¹ A "term of art" is a word or phrase that has a specific meaning in a particular field. In the appropriate context is does not necessarily have a meaning related to how those words are used in other fields or in "normal" English conversation.
² Each block in the image is six same-coloured pixels in width and height, with a single-pixel black row and column between each block.