It's safe to say コミュ障 (or コミュ症) is 100% slang. As far as I remember, it has always been used in this short form since it began to be used a few decades ago. It's never used in serious medical contexts.
The term コミュニケーション障害 exists as pure medical jargon, and it refers to the same thing as explained in this English Wikipedia article. There is an academic society for this "disorder". Many Japanese articles on this subject explicitly state that it's very different from the slang term コミュ障. However, コミュニケーション障害 is not widely known even among professional health care providers, presumably because it's nothing more than a hodgepodge of disease entities that are unrelated to each other.
Therefore, it sounds very wrong to me to "expand" コミュ障 to コミュニケーション障害. But since ordinary English readers would not understand "komyusho", I think the translators could think of no choice but to use "communication disorder".