Yeah, that's fair, it's not FOSS. Obsidian has paid services and that's how they make money (i.e. that's what the product is. They don't have your files, they don't know who you are, they don't have your email if used without services and it's not a social network - so you are not really the product in this case). The free version is marketing to get people buy the paid one, but there's no vendor lock in.