Maybe this has to do with the fact that in the comics when Shining Armor and his university friends were performing in front of a whole crowd (including Cadance) one of those goers brought his little sister, who turned out to be Vinyl Scratch/DJ PON3 as a filly and there she realized her true life's talent and got her Cutie Mark!

Sometimes when we look at the past we really surprise ourselves with the impact we made back then and how it made us what we are now, or even realize that fapping to a comatose girl makes you REALLY F'd up like you said at the time.