Apple deliberately broke DSC 1.4 to support the Pro Display XDR. Thousands of people happily using 4K HDR10 high refresh monitors under Catalina all of a sudden couldn’t under Big Sur with the release of the Pro Display, and people wondering how they were managing the resolution.

And demonstrably so - “downgrading” to DSC 1.2 actually improves those other users refresh rates and HDR support.

This is still “broken” as of Ventura.