There are a lot of old misconceptions around about cast iron seasoning. It's a layer of bioplastic formed by the polymerization when heating a thin layer of oil on the pan to high temperature - It's not about leaving your pan dirty or 'flavored'. You can clean it with regular dish soap just fine, that isn't strong enough to take the layer off.
Yes, correct. I'll add, though, that this takes skill to develop. Even the soap just left on the sponge from washing other utensils is too much. So I'll often just foregoe the soap unless there is an egregious bit of food stuck on it - which is rare as the heat is so well distributed on cast iron that I don't burn food anymore using it.
