For example, this invidious instance offers a download option for a YoutTube video, as that instance does for all YT videos:

https://invidious.fdn.fr/watch?v=lU4vv7qCQvg

Exceptionally, if you opt to download it it merely opens a player to watch realtime. While other downloads from the same invidious instance have no issues. Why is this one getting different treatment?