Daimon

Does this mean that leveling up is tied to your progress on the story or something like having level caps for each part of the story until you progress forward? If that is what this means then what is the point on doing side quests or anything else than main story if you do not want to level up each of the possible companions? I hope I have understood this in a wrong way and it just means that first few levels will come fast and after that takes lot more experience and time to achieve a level.