It does seem that not all molt are the same. Molting can be influenced by day light length, hormones, diet and the unknown. I have worked at Zoo's and volunteer at an Exotic bird sanctuary so have seen both the light molts and the very heavy ones and all are in the normal range. I have observed that a{Feel-good-000200BB} bird who is becoming mature will often have a heavier molt then the ones they have had in the past.