I could be terribly wrong, but maybe we should not take into consideration the SWSE (3x HD +CON) method and instead look at what we got from the article.
12 + CON , couldn't that mean 2 x (full) D6 + CON ?
So,
Fighter = 20 + CON , 7/level
Cleric = 16 + CON , 6/level
Rogue = 12 + CON ...