ObjectField Sprite picker: The texCoords size is always one, on Single Sprite textures

I have an editor where the user can pick a sprite to use for their tiles. When I pick from sprite sheet with multiple sprite the texCoords are correct, but when I pick a texture that is a Single Sprite, the textCoord size is always Width: 1 Height: 1

 Sprite currentSprite = GraphicsExtensions.MaterialToSprite(material);
 Sprite sprite = EditorGUILayout.ObjectField("Select sprite", currentSprite, typeof(Sprite), false) as Sprite;
 if (sprite != null)
 {
     if (!GraphicsExtensions.IsEmpty(sprite))
     {
         selectedTileMat.SetMaterial(sprite);
         saveChanges = true;
 
         Debug.Log("Sprite sel: " + sprite.name + sprite.rect.ToString());
     }
 }

Output on multiple sprite texture example: "Sprite sel: Rectangle(x:0.00, y:0.00, width:32.00, height:32.00)"

Output on single sprite texture example: "Sprite sel: (x:0.00, y:0.00, width:1.00, height:1.00)"