Nearly *all* shows are made about something no one know or care about - because most shows discuss events that haven't happened yet/haven't been invented yet.
The possibility of fans *already* knowing and caring about the events is one of the uniqunesses (which probably has as many pros as cons) that a StarTrek prequel has.
That's circular logic, which doesn't apply in this case. There's a difference between making a show with a premise no one knows about because it hasn't been seen or mentioned before, and making a show based on something that has been seen or mentioned, but that no one knows more that the initial mention.
Take the example of the "Vulcanian expedition." It was a throwaway line mentioned in a TOS episode, the context being that it was a mission that Kirk went on when he was younger, along with another member of his crew. The only inference besides these facts is the name of the expedition. "Vulcanian" implies something to do with Vulcan or the Vulcans. So in this case, there was an event mentioned and been invented, as opposed to a completely new idea.
Now granted, for all I know, Fuller and Co. can take that tiny bit of info and come up with the greatest Trek show ever, even though the above info is so vague as to be relatively meaningless as far as how they want to interpret it. I simply don't think that the "Vulcanian expedition" is what they're talking about when they mentioned a past event spoken of in TOS but never seen.
LUKE: You fought in the Clone Wars?
OBI-WAN: Yes. I was once a Jedi knight, the same as your father.
Are you kidding me? Everyone on freaking earth had heard of the Clone Wars before, because everyone has seen Star Wars a million times, and it was stuck in their brains. The "Vulcanian expedition" had no such sticking power.