Would this really be lovely? Isn't there some value in having 3 distinct formats (still picture, moving picture, moving picture with audio)? Each one is a subset of the next, but they are 3 different things that can easily be identified by what they (only potentially, but probably) are.
I can understand how you might want this feature for all the non-techies that use slack nowadays. But give me a damn checkbox to disable it at least?? Whoever made this decision deserves a real life slap