For this particular part, DS section on Electrical Characteristics 18.3 says +/- 1% typical, but as bad as +/-2 Max. I believe some of the DS's say 1% in the text of the Internal Oscillator Block section (4.5 for this one), but this particular one does not.

Hobbyists can deal with manually tuning OSCTUNE, since they are dealing with a few parts here and there, and most of the time it doesn't matter. That's not quite the same as a production environment, when all of them have to work, no matter what, and there are hundreds every day. As a hobbyist, I can throw one out (or put it in a different project) or manually tune it myself. As a manufacturer, I want less than 1% scrap, without manually tuning them. Unfortunately, M'chip does not consistently meet their spec in this regard.