Does the utf8.FullRune() has something wrong?

In UTF-8, the slice “{0xED, 0xCF, 0xCF}” should be a invalid code, but as input of utf8.FullRune, it return true.
I want to know what go wrong? Thx!

The documentation of utf8.FullRune says:

FullRune reports whether the bytes in p begin with a full UTF-8 encoding of a rune. An invalid encoding is considered a full Rune since it will convert as a width-1 error rune.

I see! thx