I'm literally making an account because it's getting so frustrating watching you post this over and over again. I'm sorry, but this advanced=master class argument just seems like extremely wishful thinking. The Polygon guy on Reddit explicitly said that master classes are not sidegrades. We don't know the growths or skills for the classes, so there's nothing firm to support either side. But final classes have never been a sidegrade in the past. Master classes have more intricate designs too, which in Fire Emblem history typically goes hand in hand with strength of the class. Every single precedent tells us that master classes will be better, without anything other than wishful thinking and poor final class diversity to claim the contrary. I really really want more infantry too. And I'm hoping there are classes we haven't seen still. But expecting advanced classes to be near master is going to leave you disappointed.
We can reclass to advanced before school phase is over. In what jrpg ever do you hit your final form before the halfway point. Also in your own example 18 stats more from 106 is huge. That's a 16% increase, that's gigantic, and that's only base stats. Please stop setting yourself and others up for disappointment.