Importing .obj files leads to different vertex orders when switching from Blender 2.92 to Blender 3.1

Question

I am a very happy Blender user. My latest project runs in Blender 2.92 and everything is working great. When I tried the new Blender release 3.1, I noticed that some of my scripts are no longer working.

I tracked down the issue to the import of .obj files. To be precise, the vertex order of an imported .obj mesh differs depending on the Blender version. For reference, an .obj file is imported using the following line in both Blender 2.92 and 3:

bpy.ops.import_scene.obj(filepath=fname, split_mode="OFF")

I also manually imported the meshes in both Blender 2.92 and 3.1 for comparison (File -> Import -> OBJ and toggled "Keep Vert Order"). The same effect occurs and the vertex order is different.

I could not find anything regarding this topic in the Blender changelogs. Is this behaviour intended? I am rather lost at the moment and would appreciate any available insight.