This is indeed a real situation, even though the audiences for long-form and short-form videos are not the same. Yet the platform’s algorithms indeed favor promoting short videos, and at the same time, most people are more willing to watch short videos because not everyone has enough time to watch a long video, whereas almost anyone can watch a short one.
It’s not saying that long videos are dead, but it’s certainly harder for algorithms to give long-form videos more opportunity to let others know.