Rerolling Champion Shards

I had three champion shards the other day and decided to reroll them. I rerolled an akali, a kennen, and someone else (can't remember who) because I didn't want any of these champs. Unfortunately, the game unlocked Kennen despite rerolling his champion shard.

Do you think they should automatically exclude the champions you are rerolling so that you can get a different champion/skin?

I would have rather unlocked someone I didn't already have a shard for.