If the tolerance stacking is running against some particular combination of mag tube, barrel, plate and magazine tube cap (or extension), it really can result in alarmingly meagre thread engagement.
Back when I still wanted to run a sling plate on an 870 that required no tools or extra time to take down, I cut my potential losses by running a Wilson +1 extension with the integral plate... whether I wanted the extra round or not. If I couldn't find a REM extension with a factory clamp today, I would go back to a Wilson or Vang extension with an integral plate. Those mag tube threads make me nervous as a cat in a room full of rocking chairs.