My library is full of 4K discs consisting of 2K upscales that still look very good. While not as good as a proper 4K scan, upscaling is fine when done well (just look at any good 1080p disc on a 4K display with excellent upscaling, they look fantastic).
I think maybe the 2K effect shots just got hit a bit hard with DNR and didn’t get any fake grain added back in to keep them consistent with the 4K portions. This is unacceptable, though:
It’s like something I’d expect from a 1080p Blu-ray 10 years ago before studios got a handle on good mastering techniques. How a shot like that ends up in a major 4K title in 2020 is beyond me, especially since the older Blu-ray looks vastly superior in comparison.