No, Dlask only pinned the factory telescopic stock so that the OAL was maintained after the short barrel was produced. Many people went a step further and bought mp5 fixed stocks as well since they fit.
Also note that Muzzle devices are also used for the calculation of OAL in the case of an NR rimfire, so while they don't add to barrel length, the barrel length is of less importance in rimfire anyways..
A good example of this is the GSG-15 SE which was initially shipped with a 25.5" OAL and was recalled to add a larger barrel shroud. (but not new barrel) to bring it back into compliance.