I understand that the Japanese emperor's speech to the Japanese people announcing the surrender in World War II was delivered in a "courtly" register of Japanese that was difficult for the populace to understand. Was that because the occasion was thought to require that level of formality, or did the Japanese emperor talk that way all of the time?
It's the same way we "code-switch" all the time when we say words out loud. We consciously and unconsciously use different words, tones, and cadence depending on the audience, the setting, the topic, and the overall context. Magnify that by 100 for public figures. Most Japanese could get the "gist" of what the emperor was saying and especially after a radio broadcaster came on to summarize the remarks. The emperor spoke "normal" Japanese in private just as a US president would not sound the same addressing a public rally as he would having a private dinner with friends or guests.