UTF does map a sequence of code points to a sequence of bytes like the other UTFs but unlike them there is more than one valid way to represent a peice of text in UTF and its output is designed to be used directly in internet mail Essentially it was a case of recognising that UTFquoted printableinsanely inefficiant encoding and doing it better by designing a single process for the entire task  From a registration and mail header point of view UTF is considered to be a character set eg its listed at httpwwwianaorgassignmentscharactersets