Oppon Reno 6 is the phone which comes with 90 Hz display but the question is why does it not support 90 fps. Actually if you want to play at 90 fps you have to use config because fps is totally depends upon BGMI (Previously known as Pubg Mobile). There are many devices which have 120 Hz display but they still not getting extreme or 90 FPS option. So If you Oppo recommend to their device with BGMI developer team it may be available in future but if you think that oppo will provide 90 fps with updates it is impossible.