This message is about possible future strategies for _writers_:
(A) Translate 8-bit characters from the local character set to
unencoded UTF-8 in outgoing messages.
(B) Translate 8-bit characters from the local character set to
unencoded UTF-8 in outgoing messages, and include the following
special header field: ...
These two strategies have exactly the same effect with type-1 readers.
The second strategy works with type-2 readers; the first does not.
Your argument is irrelevant because it assumes that is some value
in the type 2 approach. There is not.
Some of those names may be in 2047 format,
others in raw 8859/*, and others in UTF-8. A single header field,
particularly one which is not supported by everyone's user agent,
cannot handle all of those cases.
Logic error. You face exactly the same problem without the header field.
This is orthogonal to the choice of strategy.
It is pointless to choose a strategy that creates an extra header
which adds no value.