Here is a bit more information on why they think this might be possible and it comes down to the molecular structure:

So what is it about glass that makes people think it’s a liquid? It all comes down to its atoms, which aren’t arranged in a nice crystalline structure like they are in most solids. Instead, they’re all jumbled up, which you’d usually see in the structure of a liquid.

But glass is a special type of solid, called an amorphous solid, which means that it cools down so quickly from a liquid state that its molecules don’t have time to arrange themselves properly.

Which one is it?  Feel free to comment with your theories!  The debate of the 4 states of matter continues to this day and makes for a debate amongst many young and older scientists!

thanks to sciencealert for the great info