Render resolution upscaling cannot go below 1000x600?

I play on 1600x900 windowed mode, when the upscaling option first came out I had the option to go all the way down to 50% render resolution, and recently I've been having low FPS so I went to check on options and see that my render resolution downscaling is locked to a maximum of 67% (1067x600)

Even when I go to a lower base resolution such as 1280x720, I'm still capped at 1067x600, and going below in base resolution such as 1280x600 doesn't give me any downscaling options?


This screenshot is from today



This screenshot from last league


Anyone have similar issues or any solutions?