This demonstrates when the HDR400 mode is significantly brighter than the HDR1000 mode. Also, I trust this guys EOTF measurements vs HWUnboxed. This tracks consistently with all other Asus OLED's in that it is too dark down low and over brightened up top which I think is something Asus does intentionally because they think its visually pleasing.
View: https://youtu.be/RJaq8k4rKtY?si=62hf8r6UpWX803nX&t=399
View: https://youtu.be/RJaq8k4rKtY?si=62hf8r6UpWX803nX&t=399