>I take this to mean that although he was born in Ireland ...

Ouch

GBS was as well known for being Irish as for being a dramatist. At the time he was writing for the stage, he was living and working in Britain. Much of his wry humour was directed at life in Britian from the perspective of someone who regarded himself as an outsider. I suppose that the site authors were trying to get all that over in a line. I'm not sure that it is particularly easy or successful to produce such thumbnail sketches.

http://classiclit.about.com/gi/dynamic/offsite.htm?site=http://www.kirjasto.sci.fi/gbshaw.htm
http://www.workinghumor.com/quotes/gb_shaw.shtml