But no normal draft for the Twisted Treeline. Cool.

how mad are u

It's not a new map or game mode.

It's a map that was already in the game that a couple of developers added into the custom map selection list on their "free day". They had X amount of time to work on something they wanted to work on, and some of the programmers implemented a way to select Proving Grounds.

It does NOT support official ARAM rules. You can do TT Draft in customs, as well, I believe.

Correct, TT draft customs are a good way to practice too... even though you face a lot of bad players in customs.

How rustled are your Jimmies about this on a scale from unrustled to flipping tables?

It's just a Custom Game map, not a new game mode.