question about split screen on Windows 10 tablets

I was hoping someone in-the-know or maybe someone from Microsoft can shine some light on this issue: take a Windows tablet like a Surface Pro, rotate it so it’s tall/long (like you would if you had a really long PDF or something like that), for some reason, you aren’t allowed to have 1 app take up the top half of the screen and another app take up the bottom half of the screen! Even Android tablets allow this, and tablets are almost an afterthought in the Android world. Is this feature coming to Windows 10 tablets eventually? What’s the issue? I honestly for the life of me cannot think of a reason this functionality is not present in Windows tablets. (I read that is was present in very early builds of Windows 10 but removed? I don’t know if that’s true or not though)