I am actually of the opinion that more core ships should get a unique twist rather then none having some, but the twist is not a direct stat boost. So core nenzul younglings don't decay. I actually would like to see this more often for core ships. Some core raider type ships get cloaking, for example.
Keep in mind this is only core ships. So in your AI games when they use younglings you can still use gravity to slay them. At least till you get to V, but at that point, isn't it meant to hurt?