why I can't download pics from facebook at full size using python

Question

For my CS exam I have written a python code to download images from a user account using Graph APIs but I have faced a problem I am not able to fix:

When I open the pic in the browser to download it it is located at the following URL:

https://scontent.fbzo1-2.fna.fbcdn.net/v/t39.30808-6/276154675_133885455881794_6427257905137797718_n.jpg?_nc_cat=108&ccb=1-5&_nc_sid=9267fe&_nc_ohc=YLBzlwDAyFMAX-xSuA2&_nc_ht=scontent.fbzo1-2.fna&oh=00_AT8Id6JhclEoVKJSWjxj2QPFxJJV4AiyuLQRfaEP02-81A&oe=625D705A

but when I open it from a python application it tries to download the pic from a different URL:

https://scontent.fbzo1-2.fna.fbcdn.net/v/t39.30808-6/276154675_133885455881794_6427257905137797718_n.jpg?stp=dst-jpg_s720x720&_nc_cat=108&ccb=1-5&_nc_sid=2d5d41&_nc_ohc=YLBzlwDAyFMAX-xSuA2&_nc_ht=scontent.fbzo1-2.fna&edm=AJfPMC4EAAAA&oh=00_AT8deCIWQLP87HEgyDOa1GIAcGBb9L7bElubSoHzidxvvQ&oe=625D705A

and it has a different resolution from the original!

I will post here some code, if you need the full code, I can add it. this is the downloading function:

# retrieve the post id to download the image from fb posst

# download and save image from permalink url
def download_and_save_img(img_url, img_name):

    # retrieve only the img name / the file extention seams to generate an error -> setting it manualy
    last_slash  = img_name.rfind('/')
    file_ext    = img_name.rfind('.')
    img_name    = img_name[last_slash+1:file_ext]

    # download the image with a GET request and write it to an img file
    # print(img_url)
    img_response    = requests.get(img_url)
    image           = open("fl-tw-fb/" + img_name + '.jpg', "wb")
    image.write(img_response.content)
    image.close()

And here is the call

response = get_img_link_from_fb_postID(post_id['post_id'])
response_json = json.loads(response)
print(response_json)
img_url = response_json['attachments']['data'][0]['media']['image']['src']

# finaly download the img from fb and save it
download_and_save_img(img_url, line)

when printing the response_json I get:

{
   "attachments":{
      "data":[
         {
            "media":{
               "image":{
                  "height":405,
                  "src":"https://scontent.fbzo1-1.fna.fbcdn.net/v/t39.30808-6/278102009_133887052548301_9150026685369816171_n.jpg?stp=dst-jpg_s720x720&_nc_cat=100&ccb=1-5&_nc_sid=2d5d41&_nc_ohc=WF5mnEaaoKcAX9GxsvH&_nc_ht=scontent.fbzo1-1.fna&edm=AJfPMC4EAAAA&oh=00_AT9T6TUvuRni6TEcLz7oteYsH8E_6yko2FRSEXTH9MPppQ&oe=625BDBB7",
                  "width":720
               }
            }
         }
      ]
   },
   "id":"102956292308044_133887055881634"
}

Any idea?

Edit: adding code for @WizKid:

# retrieve the image link present in a given post_id
def get_img_link_from_fb_postID(post_id):

    # (extended) access token
    at  = 'xxx'  # removed 

    # build the url
    url = 'https://graph.facebook.com/v13.0/' + post_id + '?fields=attachments%7Bmedia%7D&access_token=' + at
    try:
        response = requests.get(url)
    except Exception as e:
        print(f"Error in get img link from post_id: {e}")
    return response.content