Just a word of caution, all the vibrapods I've used leech oils/residue into any wooden surface, effectively ruining any finish or surface they spend any time on. Beware. Wouldn't be a problem on glass, but they've wrecked speakers and shelves for me. I threw them all away.
More generally, isolation solutions are designed -- as you undoubtedly surmise -- to minimize the interaction between the component and the surface it is on. Thus, isolation is less dependant on the shelving material than coupling/mass-loading devices. There may be some interaction, for sure, as nothing's perfect -- but I would agree that the more effecitve the isolation, the less the interaction. Perfect isolation would make the base material irrelevant. Again, however, nothing's perfect.
More generally, isolation solutions are designed -- as you undoubtedly surmise -- to minimize the interaction between the component and the surface it is on. Thus, isolation is less dependant on the shelving material than coupling/mass-loading devices. There may be some interaction, for sure, as nothing's perfect -- but I would agree that the more effecitve the isolation, the less the interaction. Perfect isolation would make the base material irrelevant. Again, however, nothing's perfect.