Abilities have to repeat because they stats boosts are only active as long as they are in your party. If you decide to switch them, there has to be another way to get those stat boosts through other DE. I would have liked it if they made some minor loopholes though, like if you made a better version of a DE you already have, the ability links carry over.
I wasn't talking about abilities, I was talking about commands. I saw like 5 dream eaters that unlock zero gravira. I just wish there were more commands than there currently are.