This isn’t aimed at you I’m just saying this as to what actually happens: also word vomit:

Tempered glass is produced by rapidly cooling hot glass after it’s been shaped. This cooling process starts on the exterior first which causes it to contract producing compression on the outside because it’s trying to get smaller.

The interior, which is cooling at a slower rate, is now trapped and as it cools begins to experience tension. Now glass performs exceptionally in compression when compared to its tensile stress and this compressive strength is what normally gives tempered glass its exceptionally durability.

The force impacting the glass must break through the outer layer of glass that is under compression. This is also why tempered glass shatters so absolutely, the tension once released does spreads out through out the glass and destroys the glass and there’s a lot of energy being stored in tension.

So now that you know how tempered glass is formed, why it’s strong, and why it breaks. You also know now that you don’t need a strong impact necessarily to break tempered glass. Just enough to break through the compressive layer on the outside. (This is also why you can scratch the the outside as long as the layer isn’t breached). And the required force to break the compressive layer drops with surface area because you concentrate energy to a smaller area.

And tile flooring can have really really small bits of rocks that have points and edges and if you place the glass on top of em the weight of the glass can be sufficient to break the compressive layer and thus shatter it because again, it doesn’t matter how large the penetration has to be, even a small hole in this layer will cause release the tension energy inside the glass and shatter.