That's what it should be doing. Zhao only ever updates the HP for the level 10+ NPCs since there are hundreds of thousands NPCs otherwise, so as your NPCs are leveling, they are only now recalibrating with the new HP equation. Is also why I specified level 10+ NPCs in the sim news post, which is the same that occurred with the prior HP change.
Zao Nephalem Year 14 Day 81 14:07
With the new upgrade to the hit point system, I just wanted to make sure this is what is supposed to be happening. I currently have some NPCs with a racial modifier of 2 leveling from 6 to 7. When they do, they drop 48 hit points. I have a few on both sides now, the ones in level 6 are near 200, the ones that have recently leveled to 7, are 150. I guess I figured it would be applied to everybody not just when the leveled.