Yeah, it was a Japanese-American dispute. Yasushi Yamaguchi, who created Tails, really wanted him to be named Miles and was backed by Sega of Japan. Sega of America, however, wanted him to be called Tails. Their compromise would end up being that "Miles" would be his real name, and "Tails" would be a nickname. That didn't stop Yamaguchi from sneaking in "Miles" wherever he could, which is why you see the name a lot in the Japanese version.