I personally dont see any need to log in through any app especially if this app does not give any extra feature. Even if the app does not store your keays and even if it uses steemconnect !! since it is only an interface that lets you access your steemit account then why not having a shortcut of the official steemit on your smartphone hom screen as explained hereafter. I am using it and i can edit posts, write comments, add images, and do anything without the use of any 3rd party app !!
I had created a shortcut to steemit on my smartphone. It is a direct link to steemit website automatically resized to fit the smartphone screen. Anyone can shortcut steemit on his/her smartphone and logging in directly through the official steemit page. Open CHROME and log in your steemit account then hit the option buttons on the top right (the 3 dots) and tap add to home screen and you are done. below a screenshot of steemit logo (the shortcut of steemit on my home screen)