Why does this model unwrap despite having no seams marked on it? I am very new to Blender and wanted to use the program to UV unwrap a 3D Pokemon model from the games to use it as a sewing pattern. Now after watching some basic tutorials about unwrapping and marking seams I've noticed that the model itself unwraps on certain edges with no existing seams or anything and I don't know why. I haven't found any help while Googling my problem yet and am hoping I can get some help here!
This is how it looks without adding seams and no UV unwrapping, just selecting the whole thing in UV editing mode:

And this is after adding my own seams and UV unwrapping it:

This is where I got the model from
All primitive objects in Blender are unwrapped by default. So when you add your own seams and try to unwrap it, Blender discards the default UV and tries to unwrap UV according to your defined seams.
In your example, it looks like someone already unwrapped it and exported it as obj. So when you import it, you get the UVs but not the seams.