This isn't a secret code or anything; it's a standard romanization that almost everyone who learns Cantonese formally will learn. The thing is---formal education in Cantonese and other non-Mandarin Chinese languages is banned in schools in China. Mainlanders that speak Cantonese as a primary language often don't even know how to use it (I talked to a Cantonese-speaking girl from Zhuhai, and she was like "Can you show me what Jyutping looks like?" Bizarre).
It's pretty smart, and a bit of a slap in the face to the establishment, which has been forcing Mandarin down people's throats for the past 50 years or so.