There you have it. ST has always married itself to real world events, so your information serves as a fixed period of time between TV and film, and 8 years is certainly a more believable amount of time to justify the lead character's physical changes than what would be a shocking two years after TOS.
We had no orbiting nuclear weapons platform in 1968, no Eugenics War and I doubt we see a manned trip to Saturn in my lifetime. So it's just as easy to say that in the Trek universe, the Voyager
probes followed a different timeline.
It's all up to how an individual wants to interpret it.