Twitch only stores Past Broadcasts for 2 months before they're automatically deleted. If you want to keep them past the 2 months, you have to convert them into Highlights, which are affected.
So yes, this will absolutely affect the speedrunning community, and anyone else who has been using this method to archive old streams.
If you see a video-on-demand that is older than that, then that is an “upload” and not a “VOD” and thus is in-scope.