Below two methods can be used to fix dual-view effect while viewing an iOS app on big screen iPhone like iPhone 7 plus.
Method 1 :
User needs to enable "Support Google Cardboard QR Code" under Package >> Platform >> Support Google Cardboard QR Code and package. This will fix dual-view effect while viewing an iOS app. Kindly refer below image.
Note : With this method, an iOS app will be viewed only in dual-view which means user won't be able to view it in single mode.
Method 2 :
User needs to disable "Support Google Cardboard QR Code" which will open few other options. Select "Device Screen Size" as per device via Package >>Platform >>Device Screen Size and then package the app. This will allow user to view the app in both single-view & dual-view modes.
Note : User has to select "Google Cardboard Profile" based the cardboard profile (V1 or V2).