Are you referring to the Surface Duo? That was two separate connected screens with a clear physical border down the middle. No crease, but a constant divider in the middle that's ever present and obvious like the notch/pill. Imagine watching a video or movie with that bar in the middle, it would be too distracting.
The crease is not noticeable on a foldable because the brightness overcomes the reflections from the crease, unless you're tilting it at certain angles. When viewing the screen directly, as you normally do on a phone, the crease blends away. And you can still use a foldable when it's closed, like a slab phone there's no crease on the cover screen.
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