Yes—ETTR is still a real concept for RAW, but it’s often misunderstood. The idea is to expose as brightly as possible without clipping important highlights, because brighter tonal values generally contain more usable signal and can produce cleaner shadows when processed later.

But for high-contrast scenes, especially landscapes with bright skies, protecting highlights is usually more important. Once highlights are clipped, that detail is gone; slightly dark shadows often still retain recoverable information. So ETTR is most useful in lower-contrast scenes where you can push exposure rightward without blowing highlights.

For difficult landscape contrast, better solutions are graduated ND filters or exposure bracketing rather than simply overexposing.

As for why brighter areas get more tonal precision: image capture is fundamentally tied to the amount of light recorded. Higher signal levels naturally allow finer gradation above the noise floor, so shadows are more limited and noisier. Some RAW formats may also compress tonal values nonlinearly, which can further affect how data is distributed, but the key practical takeaway is: expose as bright as you safely can, without clipping important highlights.