Oh but it’s fun to theorize! And to have these little what-if’s.
I don’t personally share your view, my reasoning being that art might have clicked for you while you were 12, it might have clicked for someone else when they were 6, maybe it clicked for someone when they were 18 or 24 or older still.
Puberty/adolescence represents a big period of change in our lives as we develop though a lot of people and perhaps ponies too can make it well past this stage of life without really finding out what their “special talent” really is, no doubt that it could be very frustrating but I’d like to think that makes for good story potential.
There is no certainty that an individual will have found their way or place in the world at any specific age or age range, and I think that’s ok.