White’s offers Black a capture on the d1-d8 line. He’s now controlling Black’s options to recycle pieces and he also has a grip on Black’s last GIPF. Black must watch out for the piece on h4, and even more for Ge5. It makes that Black can’t play 1. … a1-f5;x, because White would answer with 2. i4-e4!  
1. … c1 is no solution; White plays 2. c1-c4. An attack on White’s GIPF with 1. … i3-f3 won’t do either, because White simply blocks the a5-i1 diagonal from the other side, which brings Black back to 2. … a1-f5;x.  So, the only option left is playing 1. … i1-c5, which is another way op putting pressure on White’s GIPF, but White now plays 2. i1-f5 himself, leaving Black no possibility to recycle pieces.