Question: In *Star Trek: Generations*, the actor Tim Russ plays an unnamed bridge officer (probably tactical/operations, as he's monitoring the ship's hull and systems integrity) on the Enterprise-B in the prelude. No pointy ears or eyebrows, so I must assume this character is not Vulcan and therefore not the Tuvok character that this same actor portrays in Star Trek: Voyager.

Was there ever an in-universe explanation given for this actor's appearance as someone other than Tuvok? Obviously any such explanation would be a retcon, as Generations was released a year before Voyager and so Tuvok's character didn't exist. But was there even an attempt, or is the role just dismissable as a human who happens to look similar to a notable Vulcan?

Answer: 
There actually is, the VOY episode Flashback, as someone mentions here, retcons Tim Russ's human appearance during the original series movies and explains that Tuvok was in fact an ensign/lieutenant during that period of time --- Tuvok is show to have served on the Excelsior during Undiscovered Country as an Ensign and specifically mentions later serving with/meeting Kirk and Spock.
I also feel myself bugged by his appearance because it bring us automatically to Tuvok (Voyager). But there is not any relationship. First because the guy at Ent-B was an human and not a vulcan; second because the Ent-B was commissioned almost 80 years before Voyager. So...