Calling glass a liquid misstates the phase transition

This sentence is misleading. It offers the lack of a first-order phase transition as a reason to treat glass as a liquid. A first-order transition, such as ice melting, is how many crystals become liquids. Glass does not have that sharp jump, but the missing discontinuity does not make the material a liquid at room temperature. Glass is an amorphous solid: it has the mechanical properties of a solid, and once it has solidified it does not flow on a human timescale. Panes in old windows that are thicker at the bottom were usually made that way and set with the heavy edge down. The same article later says the assumption that those panes flowed is incorrect.