Do you really need a screen protector if the main screen is only ever exposed when you’re actively using it? I’d thought the main point of screen protectors is to prevent scratching against pocket fabric or keys, or accidental drops. Foldables also seem pretty fragile that dropping it is a game over regardless of a screen protector.
These are all different options on the sliding scale of portability vs usability/screen size. Folding phones lie between a slab phone and tablets on this scale. I’d say slab phones > folding phones > tablets > laptops > desktops etc… You also of course have further subdivisions such as the iPad mini vs the iPad.
This is like the people saying, at the launch of the iPad, that tablets would fail because laptops exist.