The reported dynamic-range difference is not because of Sony’s ARW compression. According to the community answer, that difference comes from sensor design and hardware ISO behavior, not the RAW file format.

Sony’s compressed ARW starts from 14-bit sensor data, then remaps it into a non-linear 11-bit space before applying additional delta-style compression across small pixel groups. Because the mapping gives finer precision to darker tones, it does not automatically reduce measured dynamic range.

So why call it 14-bit RAW? Because the sensor readout itself is 14-bit, even if the stored file uses a compressed encoding rather than saving every pixel as straight 14-bit linear values.

In practice, “11-bit + delta compression” does not translate to a simple single bit depth like 11-bit or 12-bit. Tonal precision depends on image content. In many scenes it preserves the important information well, especially in shadows, but in difficult cases with abrupt tonal transitions or extreme edits it can introduce artifacts or reduce fine tonal fidelity compared with truly lossless RAW.

Bottom line: ARW compression can affect precision in some edge cases, but it is not the reason one camera measures lower dynamic range than another.