Well, actually, it is somewhat related in that Petite Sirah (Durif) was created "by crossing true Syrah with a minor varietal called Peloursin."
As for the Cape Code wine store "expert", picking grapes when they are smaller would mean picking them when they were not yet ripe. How would you get all the characteristics that a PET is known for if you used under-ripe fruit in the process.
Whatever happened to "I'm not sure of the answer but let me check and I'll get back to you."
They pick the grapes when fully ripe, but then shrink them in an "appareil se racornir" until they are only 10% of their normal size.
...wait, you mean this isn't the French Sci-Fi Blog? Sorry :-)