No, it really isn't. One of the stated goals of the GNU project is to develop an entirely free (as in libre) operating system. Calling Linux "GNU/Linux" allows them to say they've completed that goal, despite little details like their continual failure to deliver a finished Hurd kernel. Linux's userland isn't even primarily GNU software, and I think GNU may not even be the single-largest contributor to the core userland anymore.

AIUI the primary reason why the HURD kernel is not finished is that when GNU/Linux became generally usable, it was de-prioritized and essentially turned into a research project.