You could consider it a burn yeah, I understand that it's not good for your use case where you'd want to delegate rc to every user that logs onto peakd and then undelegate after a time, it's important to not give rc back because it opens up a lot of edge cases where an user can trick the system into having more rc than before (the rc system is not that stable, and a rogue witness not having the rc plugin enabled could leverage that, while working on this feature I found a bug that would allow someone to get a lot of rc for free). Additionally giving the rc back opens up an attack where someone can delegate rc to an user, wait for him to have less rc than the delegation and then undelegate, which means it would drain all of the receiver rc (rc is fungible so there isn't a way to tell if rc given is delegated or not).

In regards to it being better or worse than a cooldown, it's better than a cooldown because your rc starts to regenerate immediately as opposed to hive power delegations where you can't do anything with the hive power that you undelegated until the end of the cooldown