GMS v.142 - Dawnveil: Demons of Tynerum Update Notes

Modes depend on how many pieces you kill before going to head.
Kill all three (shoulders, abdomen) : easy
Kill two : normal
Kill one : hard
Kill none : hell (and this IS hell)

Any idea of the significance of the right & left torso/leg maps asides from farming the blue coins? Because I tried killing only the shoulders and abdomen (skipping the other maps via tele. rocks), and the head yielded a significantly larger amount of HP (when it was supposed to be in easy mode) in comparison to that of the head after having cleared the other maps beforehand. In other words, would you say that clearing the other maps is a prerequisite for killing whatever amount of shoulders/abdomen that would constitute the different modes of difficulty?