Why are gemstones skins not considered Legacy?

So i was looking at the new event Coming out for the Battleboss skins. And The even goes something like you buy a Orb that gives normal skin shards with a chance of gemstones,orb or Dreadnova Daruis. Then You can buy a Orb that cost 295 rp and get A legacy skin shard, With a chance of 2 Gemstones and the new legendary lancer zero hecarim. But you cant get the gemstones skins as an drop chance from the skin shard. So this doesnt make alot of sence to me. Why pay more when you could have a chance at getting all 4 instead of just the new one? Idk this is wierd and im just curious. Thanks for any help.