I'm not sure I'm convinced.

If splitting the UI is useful then it feels like you should just let me choose to split it even on a single display rather than deciding for me. My laptop has a display aspect similar to a folding phone when unfolded, so if splitting each half of the display into two panes is useful it should be useful regardless of device.

Personally if I bought a folding phone, I'm probably buying it specifically because I want a bigger display for existing content. I don't want your app to decide for me, to treat it like 2 displays. Imagine in vi or emacs auto split panes based on your aspect as shown in the article. No please! Let me choose when I want it split

And of course, Safari does not yet support this as of the tech previews.

https://caniuse.com/?search=horizontal-viewport-segments