1. i1-g3 is not possible because of 1. … i2-e2 (White must then play 2. f1-d2 to recycle pieces and offers Black the possibility to do the same on the d1-d8 line). So White plays 1. e2;xGe3. He must remove one of his GIPF-pieces, otherwise he’ll run out of pieces. The GIPF on Ge3 is the only one he can take and still be sure that Black will not get a chance to save Gd5 without running out of pieces. He needs both Ge4 and Ge5 to keep Black under pressure. It prevents Black from playing 1. … b1-d3, because that would make Ge4 too dangerous on the a5-i1 diagonal.  So he has little other choice than 1. … a3-c5.  But that doesn’t help either: 2. i1-g3 / f1-f4 / 3. h1-c4 / c1-c5;x / 4. f1-f4;xGd6 / X.
Examples of escapes if White would have removed another GIPF: