Game Mechanics: Out of combat pet regen bonus?

[kanras]

			if(!IsEngaged())
				SetHP(GetHP()+hp_regen+bonus+(GetLevel()/5));
			else
				SetHP(GetHP()+hp_regen+bonus);

When I was digging around trying to figure out why mage epic wasn't regenerating correctly, I found this. Does anyone have a justification for why pet regen is getting (level/5) extra hp per tic if it's out of combat? I couldn't find any info on this, so I removed it:

SetHP(GetHP()+hp_regen+bonus);

If you can dig up something about this (preferably classic), please post.