This is the sequence used in the professional 2010 solution of Cheng. Since 2007, when I found the second throw-in ( here) to be a valid option for Black, this sequence has been an integral part of our solution.

In 2011, the validity of the double throw-in has been approved by Prof. Jeong SooHyun ( 807), too.

White needs no move to capture Black's upper right group. All of the shared liberties are occupied here.

Black needs two local moves to capture White's group.

Relevant for the semeai is a "distance" of two moves (two for Black vs. none for White). As far as the outcome of the semeai is concerned, the second throw-in does not change the matter.