Would Knowing Mintages Of Error Coins Affect Their Value?

I don't think that knowing the original mintage would be nearly as important as knowing the surviving population. Using the 18/17 nickel in the OP, it stands to note that the avarage Joe in the 1920s wouldn't be bothered to observe his nickels closely enough to notice the error. I'd imagine that plenty got into change and turned into the dateless buffaloes that turn up in change from time to time.

It doesn't matter if there were originally 5,000 or 500,000 of these coins... what matters is how many are left, and that's not something that can be known with any certainty.