Colour hues of imported videos are sometimes unexpectedly different

OS and Version (please complete the following information):

• Operating System: Debian Trixie
• Shotcut Version: shotcut-linux-x86_64-26.4.26.txz from the project download page

Describe the bug Colour hues of imported videos are sometimes unexpectedly different even for identical displayed clip properties.

Steps To Reproduce

1. Download green.mp4 from https://www.metalevel.at/shotcut/green.mp4
2. Create a copy of green.mp4 with: ffmpeg -i green.mp4 -colorspace 1 copy.mp4
3. Start Shotcut, create a new project and append both videos to the timeline.
4. The properties of the two videos show the same value for Color space: ITU-R BT.709.
5. Yet the hue of the green differs visibly and measurably between the two clips. In the clip corresponding to green.mp4, the green value is measured as 225, whereas in that of copy.mp4 it is 238.

Expected behavior

I would expect the green hue to be exactly the same in the two clips, since the -colorspace option of ffmpeg is meant to set the frame attribute that was, according to the shown properties, apparently implicitly already taken to be bt709 for green.mp4, and explicitly set to that same value for copy.mp4.

If the difference in hues is unavoidable, I would expect one of the clip "Properties" to show a difference between one of the attributes pertaining to colours.

Screenshots

green.mp4:

copy.mp4:

Identical video properties for both clips, in particular ITU-R BT.709: