I went back to the apple store the next day, told them I didn't do anything special with it, it was just out and I never had it in my pocket or anything like that. Maybe it came out like this from the box, maybe not, I can't verify because this is pretty much only visible under bright light. Even from my home to the apple store, I put it back in the box just in case.
I really dislike screen protectors, they feel uncomfortable to use, and on my Iphone 7+ I never had any major issue with the screen like this.
I like this analogy that I saw in this forum from another thread. A screen protector is like a condom, it is uncomfortable but it helps avoid disaster.
But after seeing how easily the iPhone 12 gets scratched from youtube reviews (Dave 2D, MKBHD...) I bought a Belkin screen protector that I will pick up tomorrow morning in the App Store. They have never mentioned a scratched iPhone screen in their reviews before.
The apple store where they helped me looks gorgeous, had this whole room for me and the store employee, it was definitely a great experience.
There is a thread
HERE saying that the Apple store screen protector machine scratched the stainless steel sides when they installed it.
Now I don't know if I should let them install it or not, it seems like that guy is pretty unlucky having 3 phones scratched in different stores, but new comments popped out saying their phone went in it fine.