That wasn't the only argument though. If the data was encrypted with a facebook held private key, the user would still not be able to see it. If it was E2E encrypted with the only key being on the device, people will get mad when they reset their phone and get a new one, only to find their messages are gone.
SMS had the same problems forever, but isn't owned by a company, thus you can't blame xyz company if random apps access your SMS. No company got ever investigated by multiple nation states over that.
You still haven't addressed my main question though, how will a random app scraping your WhatsApp be any less of a scandal than Cambridge Analytica?