FPS locked at 60

The entire app is locked at 60 fps. When using the UI of the app plus the book reading page as well.

My phone is OnePlus 10 Pro 5G which has a 120hz screen. I use all apps on 120fps and anx reader is the only app that seems to use 60 fps.

On my phone's setting, there is a place where I can set specific fps to apps, I also checked there and it's set at 120 fps.