I was trying out Arc and almost forgot about it, but now knowing about this feature changes everything, thanks for pointing it out! Very often I need to see two or more pages side by side and I just hate making a mess in my browser with multiple windows open. They just tend to get lost and I have to move them out of the way or close them one by one, it is just annoying.

You can even have more than two splits, which I did not expect. Also, holding the option/alt key when clicking on a link opens it in a new split which is super convenient.