Well your 100% wrong. If any plant is harvested too early it gives a mind high, not a body stone. If a plant is harvested too late it gives a body stone.

If the plant is indica and harvested at the right time it'll give a body stone.

If the plant is sativa and harvested at the right time it'll give a mind high.

So if he's NL is giving a head high it was picked WAY too early, and therefore isnt achiving its full THC/Cannabinoid potential.