Why the nerf on Armor Pen RUNES compared to ITEMS?

I don't get it. I've invested in Armor Pen runes. You invest in runes for their stat bonuses early game. Likewise, we've established that flat armor pen is at its strongest in the early game because no one has built armor yet and innate armor is at its lowest.

So why in the world are armor pen runes being changed to lethality that breaks even AT LEVEL 12 when all of the lethality items break even at level 8?

If anything lethality runes should be breaking even at level 6 (earlier).

Anyone who runs armor pen runes took a significant hit to their early game with this change.

11.52 flat armor penetration was just changed to 14.4 lethality. Or 5.76 flat armor penetration plus 0.48 per enemy level.

That means at level 1, when armor penetration was at its strongest, you just took away HALF of our armor pen. At level 1 with runes and masteries, a typical champion would have 30 armor.

100/(100+30-11.52) = .844 100/(100+30-5.76-0.48) = .808

That's 3.6% less physical damage at level 1. It gradually improves until it breaks even at level 12, but really what do we care about? Let's consider a typical enemy champion at level 18: say 82 base armor, 9 armor from seals, and 60 armor from items for a total of 151 armor:

100/(100+151-11.52) = 0.4176 100/(100+151-5.76-0.48*18) = 0.4227

That's a whopping 0.5% extra damage on lethality runes compared to the old armor pen runes at level 18. Of course I'm assuming no other armor pen/reduction, but still I think the point is fairly clear: THIS WAS A HUGE NERF TO ARMOR PEN RUNES.

I don't want to sacrifice 3.6% damage in the early game when it could make the difference between me getting a kill or being killed, me snowballing to carry a match or me letting my enemy start snowballing to carry against me, etc... in order to get a measly 0.5% extra damage at the extreme late game. If I get even a handful of extra CS in lane / deny a handful of CS because of the extra early strength, that gold will more than make the difference up.

Why wasn't the same approach taken as last season, where mana regen runes were NOT CHANGED when mana regen was overhauled?

Armor pen runes were IMMUNE from the problem plaguing flat armor penetration: that assassins bought it when ahead but were useless when behind. Flat armor pen runes were a DEFAULT from the start of the game - you didn't have to buy them.

I see no reason why they had to be changed at all, but if they did have to be changed, shouldn't they have been made to break even at level 6, or at least level 8 like the rest of the lethality items? 12 is way too large of a nerf. I can't see how it would ever make sense to take Lethality marks over AD marks or AS marks now... Runes are meant for the early game and Lethality simply gives up way too much early.