Also outside the bounds of repeatability of the user's focus adjustment.
my black and white photos of the Mendocino Coast: www.jonshiu.com
I don't know what the heck model of Peak or whatever you've got in mind. Mine is built
like a little tank and holds focus perfectly. I've tested its accuracy with some very finicky enlargements on film etc, not just paper, and specifically cases where the difference in paper or even film thickness would be a make or break quality distinction. There is a separate reticle focus within the eyepiece to make sure you've got it properly set. A very precise instrument. There is even a separate blue glass filter just in case you're not using an apo corrected enlarging lens.
I've found the blue filter to be relatively useless with modern enlarging lenses which are
well corrected, and obviously of no value with my true apo process lenses. Some time ago I horse-traded for a bunch of drkrm equip which included some old style Componon lenses, where a blue filter might have helped with graded papers; but
I didn't keep any of these old lenses.
I have and use a Peak focuser too. Certainly, the old trusty Paterson did just fine, but it couldn't get into the corners as well. I needed that for alignment-checking and for large prints. Like many things in a darkroom, it isn't a "must have" but is a "good to have."