Take any diagonal matrix. Then the eigenvalues are the diagonal entries but the the Gerschgorin discs are points centred at the diagonal entries. So we can't remove one of the discs from the set.
This is false
Take any diagonal matrix. Then the eigenvalues are the diagonal entries but the the Gerschgorin discs are points centred at the diagonal entries. So we can't remove one of the discs from the set.