Highlight preservation mode inconsistency from V5.4.1 to V5.6.0

Is there an existing issue for this?

• I checked and did not find my issue in the already reported ones

Describe the bug

I have a library of images edited in V5.4.1.
On loading these into V5.6.0 they appear over-exposed. The 'highlight preservation mode' control in the exposure module is visible, and ticked.
In V5.4.1 I had never seen this control.
I have to go through and manually untick this to restore my previous edits.
I have checked by loading the same previously edited images into the V5.6.0 AppImage (over-exposed, control is ticked), then back into the V5.4.1 AppImage (correct exposure, control is hidden).

Images are all canon RAW, with AutoLightingOptimizer=Standard (ie ON, with moderate effect).

Steps to reproduce

1. Edit a qualifying image in V5.4.1 (Canon RAW with AutoLightingOptimizer=Standard )
2. The exposure module does not show the 'highlight preservation mode' control
3. Load this image into V5.6.0
4. The exposure module shows the 'highlight preservation mode' control, it is ticked and the image is over-exposed compared to the same image in V5.4.1.

Expected behavior

darktable should be consistent with previously edited images between versions.

Logfile | Screenshot | Screencast

No response

Commit

No response

Where did you obtain darktable from?

darktable.org / GitHub release

darktable version

5.6.0

What OS are you using?

Linux

What is the version of your OS?

ZorinOS 17.3

Describe your system

Wayland, 16GB RAM

Are you using OpenCL GPU in darktable?

None

If yes, what is the GPU card and driver?

No response

Please provide additional context if applicable. You can attach files too, but might need to rename to .txt or .zip

No lua scripts

Reproduce the issue in darktable 5.4.1 and 5.6.0 using a Canon RAW image with AutoLightingOptimizer=Standard, comparing the exposure module and rendered exposure. Start by tracing the highlight preservation mode behavior across those versions; done means previously edited images retain consistent exposure without requiring manual control changes.