That's maybe a bit far-fetched, but couldn't this be a typo? The book mentioned should date back to 1980-81, right? That's about the time when the first T-72s should have become available in GDR if I'm not mistaken. Couldn't that have been about these first T-72s? In 1980, the T-62 wasn't exactly the most modern of Soviet tanks anymore, even for the NVA.
Could you tell us what the original sentence was?
And that's good to have first-hand sources!
May I also ask where your Grandfather served, out of curiosity? I mean, the result wouldn't have been the same if he heard about the T-62 while in was leading a tank unit or, say, in Versuchstruppen or material command.
Thanks for the sources anyway!