Sort:  

Not really... I would say you got it right for the wrong reason.
It is that before 30 minutes the author gets a portion of the curation.

At 0 minutes, the voter gets 0% of the curation vote.
At 3 minutes, the voter gets 10% of the curation vote.
At 30 minutes, the voter gets 100% of the curation vote.

But, if you could get 100 Steem * 10% for voting at 3 minutes
as opposed to
Getting 2 Steem * 100% at 30 minutes, which would you do?

This was implemented to "give humans time to read the post"
So that bots wouldn't vote at 0.001 seconds after posting.
Not sure if that worked out all that well.