rerolled king tryn shard and 2 others....and got....king tryn...

So I just rerolled a king tryn shard along with 2 other shards and I got king tryn permanant. I just think its kind of stupid that I get one of the skins that i was rerolling. I mean obviously I didn't want that skin since I was rerolling. imo I think that made the reroll pointless because I could have just disenchanted that shard and got one of the others. So riot whats up with that?