[RPG] Are Monks proficient in Darts

Everyone is proficient with their own unarmed strikes

In the errata for the Player's Handbook, the Unarmed Strike entry was removed from the weapon table. However, the rules on Unarmed Strikes in the combat section now say that every character is proficient with unarmed strikes (emphasis added):

Instead of using a weapon to make a melee weapon attack, you can use an unarmed strike: a punch, kick, head-butt, or similar forceful blow (none of which count as weapons). On a hit, an unarmed strike deals bludgeoning damage equal to 1 + your Strength modifier. You are proficient with your unarmed strikes.

Yes.

Regular monks weren't given proficiency with monk weapons. That FAQ applies to them. It isn't about the Unchained monks. As you note, it's old, and Unchained monks didn't even exist at that point.

Unchained monks are given a weapon proficiency with any monk weapon, hence the bit you bolded.