You know, I started this... But, it appears as though the "glass is a liquid" MAY be an Urban Legend... I got to thinking about my OP on this, and then remember hearing somewhere that it might not be true, so I did some searching:

Scientists aren't in agreement on this, BUT:

Most agree that glass is actually an amorphous solid, rather than a liquid and,

There is a belief that the reason why old glass is thicker on the bottom is that glass making was very imperfect, and the heavier end (thicker end) was installed on the bottom because the panes were more stable that way...

Oh well!