I guess the proper way to phrase it is that "Glasses" are amorphous solids, that is, they don't have a regular shape.
Therefore, while they have properties in common with liquids, but are not liquids. The flow effect of glass may be observed in the lower grades of glass, but not in the higher grades of crystallized glass.
FWIW, the program did not state whether the glass fall out over time was due to any flow or simply a deterioration over time of the grout, sealants or whatever was holding the glass in place or of the glass itself. It was simply my assumption. Sorry.
Just correcting a pet peeve.
I’d expect sealant deterioration and simple random breakage over time. Lack of repairs accelerate adjacent deterioration.