Opinions on Glass Shelves

I am thinking about buying a new audio rack. When I tap on the shelf below the shelf on which my turntable sits while the needle is on an LP at rest, I can hear the a slight echo in my speakers.

I’ve looked into various audio racks including some from Billy Bags. The salesperson at Billy Bags told me that their ¾” cracked glass was sound-deadening and would provide excellent sound isolation. To me this is counterintuitive.

Has anyone had any experience with cracked glass from Billy Bags?

Has anyone had any experience with glass shelves in general?