Hi Michael I'm really not sure what the current NRCA or the CABO (http://www.cabo.org/) has to say, if anything, about sealing the roof side of chimney's. But I'll tell you what I do....I build a cricket. It takes a bit longer, but in my experience, it is the only sure way to keep moisture from going retrograde under the shingles and penetrate the roof to chimney flashing. On steep pitches (12/12 or greater), all building has to be done off toe boards which makes any kind of construction difficult and time consuming.
Not to sound like an alarmist, but with that steep pitch I'm surprised they are not using copper or at least aluminum for wrap flashing. There is going to be some fairly serious flashing bends to seal those chimney corners, unless it is prebent/welded beforehand, which I would doubt for galvanized. And anywhere the galv covering is cracked (as in a sharp bend), that is where it will start rusting....sometimes within a couple of years.
Sorry I can't be of more assistance. Perhaps an experienced roofer, current on building code can speak to this.