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 , 5/level
Wizard = 8 + CON , 4/level (?)
Question, does CON adds on levels beyond 1st? It's kinda of a dumb question i know, but ... from what the article points out, it doesn't seem so.
Also, on another note, jumping into precipitated conclusions, if you follow the above, and a CON of 14, you'd get 120HP at 15th level (for a fighter).
(20+2) + (7*14) = 120
Anyway, as i said, i could be terribly wrong, and i probably am.