Reactivating naturaRegeneration after loading a world fully heals when sitting on a horse on peaceful

(NEW) YouTube-Video: http://youtu.be/IrUtk9wfT2M

Say the new gamerule "naturalRegeneration" is deactivated and you are hurt (like having 3 hearts left).
Now when you reload the world (singleplayer), sit on a horse and you reactivate "naturalRegeneration" the hearts just refill within 1 second.

tl;dr:

• Play in peaceful
• naturalRegeneration = false
• You get hurt
• Reload world
• Sit on horse
• naturalRegeneration = true
  => You immedeately have full health instead of regenerating half a heart in ~1 second