Just noticed something that was overlooked now that the Challenges page has been reorganized. In the "You Graduated!" challenge, the requirements are stated like this:
"Awarded to a player who completes 14 of the 15 New Player mini-challenges."
However, there are actually now a total of 16 such mini-challenges (and they aren't called "New Player" but "Intro" now, apparently.) The top of the description has that correct number, but the bottom does not (under heading Requirements