''Looks like exhausting 70-80% of my origin power had a positive effect on my overall origin pool."
It's like when an athlete uses up his stamina before resting, then, the athlete would experience a slight increase in his stamina. This applied to Nemesis's origin power training, other origin masters also experienced this effect. Except for those who hit their limits, this effect generally appears for anyone who did that.
It's a common knowledge among thel but not many if not a few would never experience the improvement Nemesis had, not even if they used their entire life to continuously exhaust and recharge themselves.
Aside from the perks granted to her by her mixed bloodline between angel and demon, most importantly, it was just the compounding effect from her already humungous origin power reserve. It wasn't easy to deplete her already huge origin pool. If she didn't plan properly, she would have recovered origin power faster than she could spend them.
