Dont know as I havent downloaded it, but I'm guessing it streams the main stream instead of just the Extra low-res stream . Frankly on a phone I dont see the need..
FWIW I only see 2 versions on iPhone from Dahua, I wouldnt trust the others...
HD are the tablet versions. Plus includes push notifications. Any version can stream high-def. You choose primary or extra stream when setting up the site in the app. Check out the software section of the wiki... https://dahuawiki.com/Main_Page