I am not going to discuss what is the optimal squeeze play for the overtrick. This is the coldest slam even that Mrs. Bridgewater, the little old lady who just play the game not to revoke, or the boss of Orttaman Foundation in "The Principle of Restricted Talent", would not blow.
However, GIB simply tried to be too cute, and eventually it backfired.
At about trick 9 I claimed - which GIB wisely refused but...