I have a theory on how the Gatorskin "works".
whever I've excavated bits of glass out of the tread, rather than sharp shards or chunks, I get little spherical balls of glass. My idea is that the glass is sooked up by the tyre into the thicker rubber, but can't get further in past the puncture-proofing belt. It is then crushed repeatedly as the tyre rotates and deforms and reforms thousands of times per hour. After a while the action will leave you with smooth balls of glass (much like pebbles on a beach), which will eventually be crushed to nothing and leave not much trace to dig out the tyre.
Then again, that's just a theory.