OK, but that makes perfect sense given utf-16 was actually quite widespread in 2003! For example, Windows APIs, MS SQL Server, JavaScript (off the top of my head)... these all still primarily use utf-16 today even. And MySQL also supports utf-16 among many other charsets.

There wasn't a clear winner in utf-8 at the time, especially given its 6-byte-max representation back then. Memory and storage were a lot more limited.

And yes while 6 bytes was the maximum, a bunch of critical paths (e.g. sorting logic) in old MySQL required allocating a worst-case buffer size, so this would have been prohibitively expensive.