I am using Iphone 5s IOS 9.1.
To check this problem build an IOS with landscape target version 8.0 Cordova CLi 5.1.1 test on mobile. The portrait images are showing in the splash screen instead of landscape.
ok, the 1334x750 landscape splash screen is not supported in Cordova, the placeholder in XDK is not valid.
Landscape splash is only supported in iphone6+ and iPads. If u want landscape splash for other iphone sizes, u have to create landscape splash and rotate it to portrait and add as portrait splash screen in XDK, let me know if this makes sense?
I looked at your 1334.png, just rotate that to portrait and add as portrait splashscreen in project settings
your 1334.png is 1334x750, rotate the image (not scale or stretch) so that it becomes 750x1334
I tried an app with your splash screen image on iPhone6 built with cli 5.4.1, orientation=landscape, fullscreen=yes . Seem to work fine for me, let me know which device your testing on and other settings. If possible send me your zipped project in private message I can look at it.