I don't know, I'm pretty sure he was referring to himself as the third type of person when he wrote that:
http://www.theguardian.com/books/2014/sep/24/terry-pratchett...
http://www.theguardian.com/books/2014/sep/24/terry-pratchett...
The last part, as you note, is:
"And at the other end of the bar the world is full of the other type of person, who has a broken glass, or a glass that has been carelessly knocked over (usually by one of the people calling for a larger glass) or who had no glass at all, because he was at the back of the crowd and had failed to catch the barman's eye."
...and both quotes are offered in The Truth, which offers more than a few critical comments around the glass-should-be-bigger set.