There's no device profile to set MobileContentScaleFactor for iPadPro 10.5". It picks up other rendering settings properly from the iPadPro family, but this doesn't set MobileContentScaleFactor.
This was testing on iOS 11 beta.
1. Package StrategyGame for iOS
2. Install to an iPad Pro 10.5" and run the app
RESULT: Noticeable pixelation compared to iPad Pro 9.7"
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-47906 in the post.