How? Spock's quirks (touch telepathy, mating cycle, being son to the Ambassador) were all extremely public things from the Vulcan point of view - every single Vulcan would have known all about all of them. That Spock's colleagues don't requires the entire planet Vulcan to be isolated from Spock's colleagues, then. And, by extension, from the rest of the universe, because Spock's colleagues enjoy especially easy access to the rest of the universe.
Timo Saloniemi
Timo Saloniemi