That’s a different claim and one with severe tradeoffs for the other option: you can regain access to your Dropbox after losing your password.
Since you’re running their software, you’re ultimately trusting their policies anyway. Even if they had encryption at rest it wouldn’t tell you that it’s correctly implemented and doesn’t e.g. leak keys.
https://www.theregister.co.uk/2011/05/16/dropbox_ftc_not_goo...