I would think it is like this because of permissions in Android. When a file is created it gets an "owner". In the file manager you can't see that information (3rd party file managers probably can).
For example, I can see the owner of a picture file I took, if I browse the gallery with Aves gallery it tells me that the owner of the picture is: com.google.android.GoogleCamera
That is because I took the picture with that app. And if I take a picture with the default camera, the owner is: app.grapheneos.camera
I would think that the owner of the file does not change, regardless of where it is or how it is changed. It is probably not Vanadium that tags the file...