iPhone 7+ Native IOS screen recorder is much better than iPhone 12 Pro Max

I own a 5year old iPhone 7+, it has a native resolution of 1920x1080 and if I record my screen using the native IOS screen recorder, the video resolution is 1920x1080. If I edit the recorded video using iMovie, I can save it as 1080p

Now, I own the latest iPhone 12 Pro Max with native resolution of 1284x2778 and if I record my screen using the native IOS screen recorder, the video resolution is only 1920x888. If I edit the recorded video using iMovie, I can only save it as “720P”!

I believe that the native video screen recorder of IOS has a maximum of 1920x1080 video resolution and it automatically downscale if it goes beyond that and it’s also preserving the aspect ratio of the screen meaning that the iPhone 12 Pro Max if downscaled to FHD can only have a maximum resolution of 1920x888

My question is, why Apple let this happen? Why the 5 year old phone has better result using the iMovie than the newer and most powerful iPhone? 

Can Apple update the iMovie app to still let the iPhone 12 Pro Max save 1080p FHD even if the recorded video resolution is only 1920x888?

This ia really frustrating when you expect the newer Phone should be better than the old one