You haven't leveled up until you've leveled up normally, got to Level 20, and got the cape mission that ambushes you with a bunch of Tsoo. Especially if you don't know it's coming.
Or did Synapse TF without knowing about Babbage.
That's an interesting perspective. I leveled up back in I3/4/5 well before AE. But there's so much to experience in game and there's so many ways to do things that I'm cool with anyone doing anything to level up. Sure they might not have the experience, or whatever, but sometimes the fun is teaching a player new tricks too.
Also, back in the day when I played through SquareSoft games like Final Fantasy 3 (6-Jap), FF7, FF8, FFT and the Chrono series, I often times found a nice spot to take a break from the story and level up my characters. In Final Fantasy 3(6) I found out about the Brachiosaurus in an old Nintendo Power guild and I leveled up all my 14 characters to level 99 while mastering all magics while acquiring every Economizer I'd ever need. Then of course I soundly trounced Kefka. But that was back in the day before responsibility or college.
So I'm sure if I had nothing better to do I'd probably level to 50 as fast as I could while getting important contacts like the one in Croatoa for the Katie TF. Actually taking the time to type this post was more free time than I should have given myself.
But, back to the topic: I'll do incarnate content and Ritki Mothership raids with my 50's if possible, and if not I'll reserve a few names of my 50's and favorite characters.