Yes, this is an important change. Right now, a portion of the curation rewards for votes within the first 30 minutes after a post is published go to the author instead of the curators. In HF20, the 30 minute window will be reduced to 15 minutes, and the portion of the curation rewards that previously went to the author will instead go back to the rewards pool.

It's a bit of a difficult change to conceptualize, and even if you understand it it's hard to predict how exactly things will change after it's released. But the main point is that it removes the incentive and advantage for authors to upvote their own posts immediately after posting.