You're completely in the right to worry about your privacy. I also agree that submitting rules that the browser can enforce without revealing any data to the extension is the proper API for 99% of extensions out there.

However, uBlock Origin is such an important extension that these limits shouldn't really apply to it. I think it's so useful and important that it should be a standard feature of every single browser out there, if not entire operating systems. The problem is browser makers are deeply involved with advertising and we can't trust them to implement ad blocking features due to conflicts of interest, so we have to trust uBlock Origin for now.