Foldable phones are fragile. That’s what a lot of people think, and while I don’t think foldables are as delicate as their reputation implies, you should protect a folding phone in the same way you would any other.
I hate display scratches, even minor ones, so I always use a screen protector and a case with every phone I have. Then I got the Motorola Razr Fold, and that changed. Not because it’s a phone that doesn’t need screen protectors, but because it’s almost impossible to find quality accessories for the phone.