Longer videos are receiving a boost in their News Feed presence, though only if people actually watch them. Facebook says it decided the “percent competition” figure should mean more when a video is longer. Therefore, long videos that hold a user’s attention will appear higher in the feed on average.
As we continue to understand how our community consumes video, we’ve realized that we should therefore weight percent completion more heavily the longer a video is, to avoid penalizing longer videos. – Facebook
Facebook is moving closer to YouTube than Instagram with changes like this. It’s promoting long-form content over the tiny videos that populate some other networks.
The company recognizes not all content needs to be long, so short videos won’t disappear from the feed.