Well there's the one I calculated from my entire credit history and then there is Equifax's version which calculates only the current accounts and the closed ones from the past 6 years. The difference is phenomenal - 10 years to be exact! Equifax's is the one the my score is calculated on, mine is... well... just for my own reckoning. 
I did some checking on another website and the graphs that a user posted suggests that there is a diminishing boost to your score on the 1st, 2nd and 5th years of your AAoA and perhaps even a very slight boost at the 10th year. [I can't post the website, graph or user because apparently that site has been banned from MyFico.] If that is the case I should see a slight score bump (1-2 pts) when my AAofA from Equifax reaches the 5th year later in October.
Starting Score: EQ 732 October 2007; Current Score: EQ 839; TU 865, July 2022;
You could be absolutely right, because I just got a score bump of 1 point to 675 - it would EXACTLY co-incide with the date of my original auto loan.
Just to be clear -- it is when your AAoA hits the 1, 2, 5, 10, 15 year milestones that you MAY see a increase in your credit score -- not the age of a single debt or of your oldest debt.