Granted it might be faster (though looking at Geekbench scores between budget Android phones [0] and the 5-year-old iPhone XS [1] I’m not overly convinced of that either), but the price of manufacturing “nice” doesn’t drop nearly as fast as silicon.
Budget phones often compromise on build and camera and screen quality (even though the latter two often look great on spec sheets) and I think the average person would notice that far more than raw performance.
https://browser.geekbench.com/v6/cpu/2900039
Aside from all the other problems a genuine pixel 3 (or iPhone XS) battery is bellow 3000 mah, so like replacing your redmi battery with a defective one.