Any Youtuvbe SEO expert will tell you that engagement with videos is key to organic promotions. People skipping ads lowers the engagement dramatically. My own experience and other media buyers talking, no sources. If you want to warm up youtube organic with ads, use discovery, since people who click on the ad voluntarily are likely to watch till the end. But in-stream people skip a lot, we're talking up to 70%, and that doesn't signal anything great to SEO part