I understand your question, but the problem is that ICG does not define their Guarantee of authenticity which forces me to look at their guarantee on grading.

If you look at all the disclaimers which they make, one must believe that the same disclaimers will apply to their authenticity guarantee.

The most fundamental issue being that as soon as you remove the chip from the slab to examine for authenticity yourself, you now face the prospect of being told that the guarantee is no longer valid after the slab is removed (after all you could have switched them)