I think that's only for the Wi-Fi printing. The HP smart app is terrible and makes you sign up for features that work on a local network. I just visit my printer's internal web server with a desktop user agent to show the "remote scan" features. Printing over local Wi-Fi doesn't need the HP Smart app, just the HP print service plugin that doesn't require login (and also conveniently enables USB printing, if you want to use an OTG dongle with your phone).