I believe that you experienced what you say you have, but that is not a "guarantee" that others will experience the same.When I first started out, I didn't have any screen protector. I coddled my 9.7" iPP and had a Smart Keyboard cover on it. Was very careful about putting it in its special pocket in my backpack and using only a clean microfiber cloth to wipe it off. Guess what? It got scratches on the screen. No matter what you do, I guarantee you'll have scratches a year in. So when I got a replacement iPad after software issues, I put a tempered glass screen protector right on that baby out of the box. Quite frankly I love it. The oleophobic coating on the protector makes it really nice and smooth and not a fingerprint magnet like the screen without it. Whenever it gets a little bit worn down and fingerprinty, I just buy a new one for 9 bucks. The Apple Pencil still works perfectly. Most importantly, the screen underneath is in factory condition. Don't listen to the people saying not to get one. The reasons not to are really pretty flimsy.
Prior to using a matte protector on my 12.9 Pro, I never used a screen protector on any of my iPads... going back to day-1 of the iPad 1 release. I never experienced any scratches on any of my iPads.... even when using styli that have a reputation for catching grit on their disc and causing scratches. The only reason why I started using a protector was because with the Air 2, Apple changed the coating on the screen. By all means, if one is worried about their screens, go ahead and apply a protector, but peddling fear is not helpful.