I consider myself fairly well educated on WW2 but Ive never heard that the soviets had plans to attack germany so soon. I was under the impression, that the soviet union planned to attack germany but like 1-2 years later than germany attacked them...
It is not true.
The hypothesis that the Soviets were going to imminently invade Nazi occupied territory is known as the "Suvorov debate", "Suvorov hypothesis" or "Icebreaker theory" after a defector from the Soviet Union called Vicktor Suvorov who wrote a book called Icebreaker in the 1980s when the Soviet Archives were mostly closed.
Since he wrote, the Soviet Archives have become open and the historical consensus is that there was no serious plan for the Soviet Union to start a war in 1941. David Glantz among other prominent western historians of the Soviet military have fairly convincingly refuted it. But your grandparents aren't dumb for having these views, they are are plausible enough that serious historians have devoted a lot of time to (successfully) refuting it.
Our moderator and attack-in-prep expert /u/Georgy_K_Zhukov has a couple of full posts laying out why this theory is debunked here and here