That's not what split tabs feature is about. Any browser can open multiple windows, hiding UI is not the important part. The ability to combine splits into groups, and doing so quickly, so you can switch between a tab that has a full screen page, and than a tab that has 2 splits in it, and maybe another tab that has 4. Of course you can open 5 windows, assign them to different spaces, resize them how you need. That's just a lot of friction.
But friction is the word I would describe my general experience with Orion unfortunately.
Just wish there was a browser I could switch to from Arc. But seems like ease of use is not the priority for Orion at the moment.