Really? Since you have often declared your distaste for anything Apple, and you have stated you would never use Apple products, how would you possibly know how split screen is implemented in iOS, whether positive or negative?
Not only do I use iOS split screen on my iPads, I mirror it to a secondary monitor for my Mac. Then in combination with other Apple tools like Drop Box I can share both files and settings as I designate (inclusive of designated receivers for specific files) to devices connected to our family server, whether they be Mac, Windows, or Android. This cannot be accomplished from any Android or Windows device, as easily, or as elegantly. The format of those files is irrelevant, whether music, video or text.
If I am using an iPad to access the forum, I can open, read and respond to a thread in one split screen while keeping the forum view open in the other. Try that on an Android device or a MS Surface device. I guarantee you will spend endless hours trying to do the same. And I am not speaking of multiple tabs but simultaneous viewing.
All this is secondary to the OP question. A complaint about how secondary windows open with a gesture, interfering with primary use at the moment. This is not a split screen issue, something which as a non iOS use, you failed to recognize. And yes, it can be a PITA for users not familiar with the new iOS gestures and how to control the results, because the secondary window covers part of the primary window. It is easy for the user not familiar with new gestures to inadvertently open a secondary window, either with notifications or settings, or something else. But again, this is not split screen, and issue resolves as the user either turns off gestures in settings or gets accustomed to the gestures as another interface control mechanism. It has its uses for those who want to enjoy those uses, even for something simple like news or equities updates while performing other tasks.