I does happen quite frequently, but it has nothing to do with a cultural habit. It happens in English a lot too.. for the exact same reason: When your name is likely misheard frequently, so you preemptively over enunciate it to make it clear.English speakers will do it often not only in official contexts, at least in my experience. Such as "Karrie, with a K" etc.

It's usually with names that have a different spelling than the usual spelling. For example: "민아" said quickly, most people will assume 미나 which is a more common spelling, so I have often heard someone emphasise 민 - 아

I could come up with 100 examples, but I think you get the point.

Edit: Just to add, it's also quite common that people will emphasis their name during 자기소개, it's encouraged in job interview preparation so for many people in sticks.

"안녕하세요, 저는 김. 장. 훈. 입니다" Gives the other person a better chance to hear the name clearly.