I tested the Samsung one in the store and that groove thing in the screen would drive me crazy

I have a google fold 9 for a year and I've never noticed it unless I look at the phone from the side. It's interesting that this is the criticism that comes up the most here where it's already been a solved issue

You think it’s solved - many people disagree.

Who havent used one

They have a nightmare of a crease. Every single one. Even slight warping causes me to recoil. No, I've used one, they are absolutely unusable for me.

You can't see the crease anymore. Source: I own a pixel folding 9 pro

If you hold it up to light to get a reflection, you are telling me there's zero perceptual warping of that reflection around the crease? None? It's as flat and perfect as a single sheet of glass?

I'd agree if there were fewer compromises required to pull it off.

What’s the main use case of this?

A pocketable tablet that is also your phone.

so what do you use on yours with more dexterity than without it?

watching videos and reading PDFs (whitepapers) are the two big upgrades, being able to take selfies and see yourself is often useful also