The requests that Telegram makes should be over https not http. If the links that it passed to create the gallery were https, a mitm wouldn't even know they are

The requests that Telegram makes should be over https not http. If the links that it passed to create the gallery were https, a mitm wouldn't even know they are requests for images. He'd only see a timestamp, destination, port and request size. There are ways to obscure these requests, the article gives some suggestions.