The logic still stands. What makes something a "kit" specific trait and another thing an "item" specific trait?
I think most people would agree that increasing power is almost always an item specific trait - you purchase AD, AS, and AP. Getting free AD/AP without purchase (think Rengar/Veigar) is always a bit troublesome, and irks some people the wrong way.
But just like increasing power, increasing defenses is also a very "item" specific trait, with very few champions who have it imbeded in their kit. The champions with lifesteal/spellvamp as defensive traits in their kit were/are notoriously hard to balance - Soraka, Vlad, Akali, Morde, etc. So you might say its a "kit" trait, but I say that lifesteal is more akin to item specific traits than kit specific.
You might say removing lifesteal is 4/10. Its not. With the popularity of lifesteal, its closer to an 10/10. Its one of the things the entire game revolves around. Changing the Dragon to Drakes was a 4/10 in terms of how extreme the idea was. Disabling lifesteal would be 10/10, as would removing other purchasable traits.