Is it okay to leave out unnecessary launch images?

Question

I have an app that supports only iPhones running iOS 10 or above.

I added only the following images:

• Default-568h@2x.png
• Default-667h@2x.png
• Default-736h@3x.png

I left out:

• landscape, since I assume iOS will use the portait one if landscape is missing.
• iPad, since my app supports iPhone only.
• 3.5-inch iPhones, since I require iOS 10, which doesn't run on 3.5-inch iPhones.

Unfortunately, my UIWindow size is 320 x 658 points on the iPhone 7 Plus, rather than the 414 x 736 it should be. iOS thinks that I support only 4-inch screens, so renders my UI at that size and then expands it, making everything looks huge.

How do I fix this?

I'm not using storyboards or xibs. Please don't suggest that I use them. That's offtopic for this question.

When the above didn't work, I tried adding Default-Landscape-736h@3x.png, but it didn't help.

I also tried using an asset catalog, but that didn't work, either, as discussed in this separate question.