Not entirely, they're also in what comes in contact with the strings, and a pick does just that. Those who have not used an Eric Johnson signature pick may assume it's the same item as the usual Dunlop Jazz III. They are indeed similar, but there are specific differences that I personally appreciate w. the EJ pick.
The nylon material is 'quicker', meaning it recovers back to its resting state sooner. The surface is not as glossy and the embossed text provides good grip. And last, but not least: the tip and edge is pointier so that it releases the strings better.