I don’t think Twitter ever really exposed this feature. I never even saw where you type in the latitude and longitude. There’s a button to use the supposed location of the device but it’s not immediately clear to me how that would work or why someone would want to do that. Assuming it’s a phone, people reading the tweet will see exactly where in the world the person was standing when they tweeted? Or a desktop computer with no GPS hardware and VPNed through Belarus is going to geolocate itself somehow?
Agreed. I loved this feature, but nothing exposed it! I think one of the ancient Twitter clients like Twitterific, or something, would do it and do reverse geocoding.