Thanks Scott for your response,
Then, If I understand it right, the spectrum is based on velocity/specificity of the ME exercises. So the Gym ME and bounding ME programs would be in a similar place in that spectrum.
However, Briguy got the point and debated a question which I am not sure yet:
Is the gym-based ME program worthwhile even if you have access to long/steep hills (to do the bounding ME workouts proposed in the Uphill Ath book, not the very heavy uphill carries you mentioned) as stated by Briguy?