Status messages should be communicated with no unnecessary ambiguity both internally (where unicorns may be the clearest term) and externally (where it is not).

Lack of clarity during periods of heavy human workload is a common cause of e.g. plane crashes. Operations people of the internet would do well to learn from mistakes made before the cloud was a thing.

If you get bent out of shape over some pretty mild slang, there are loads of companies out there who'll take your money for as staid a response as you'd like.

If you don't already know that "unicorns" means in this context, then you are not a GitHub user, and thus it being down is not a "high pressure environment".