The story as I understand it is the whiskey that started as the 13yo but by the time it was put into the tank it was about 18 or 19years old. The original whiskey was some 13yo Medley rye. Julian purchased enough to do a bottling one year just to see if he could sell a rye whiskey. He was doubtful that it would sell, but he really liked the whiskey and decided to take a gamble. It paid off and was a hit. He purchased some more with the option to get the rest of it later. The brand continued to grow and rye whiskey was beginning to take off big time. He went to purchase the rest of the whiskey and Diageo renegged on the deal. Julian added some pressure and they Diageo said they would sell him some Cream of Kentucky to fill the amount of the order and Julian agreed. He stored the rye in his warehouses and bottled from that stock but it continued to get older until he decided to tank it and ration the rye until he could get some aged rye on line from BT. The whiskey was like 18 or 19 years in the barrel, but he did not want to change the label every year, so it is the 13yo Family Reserve Rye on the label. By not changing the label, he also does not have to wait as long for new stocks to age.
I will not guarantee that this is 100% accurate as to how it went down, but it is what I have heard from various people and about as accurate as you will probably get in this industry.
"Our people live almost exclusively on whiskey" - E H Taylor, Jr. 25 April 1873