When you decheck it, the blurry goes away and it feels like 60fps. When you check the box to limit to 30 fps on PS4 pro, then you get that same blurry effect with the camera. Much to my chagrin, a major focus of the PS4 Pro is 4K support, but not all PS4 Pro-optimized games are going to support it.
The PS4 pro runs and looks great on the same tv, no blurring effect when you move the camera. One thing a lot of tech savvy people have been saying is that the PS4 Pros specs dont seem to put it in the proper league to run games very well at native 4K. Maybe it is running close to 50 but that blurry effect messes with my eyes, I completed all the levels on my original Xbox before I got the X and I don't remember that blurring effect, same tv just now it's in 4k. This makes the Xbox version feel like it is less fps. Performance is the focus in this case, and thats more than enough for Dark Souls III, with the locked 60 FPS setting being a marked improvement over the base PS4. The main difference I notice is on Xbox one x when you rotate the camera everything except the truck blurs as you move the camera back and forth, the trees and grass the buildings even the ground around the truck, it all blurs when you move the camera, it does not do this on PS4 pro.
When I check the box to limit to 30fps on PS4 pro that matches exactly how it runs on Xbox one x, it doesn't feel anywhere near 50 fps on Xbox one x.