"tee -" treating "-" as stdout violating POSIX?

[Bernhard Voelker]

"tee -" duplicates stdin to stdout (maybe in interleaved order)
since v5.2.1-1247-g8dafbe5; this behavior is documented as such.

But POSIX explicitly mandates different behavior:

  http://pubs.opengroup.org/onlinepubs/9699919799/utilities/tee.html

  If a file operand is '-', it shall refer to a file named -;
  implementations shall not treat it as meaning standard output.

I assume it's too late to revert the behavior to adhere to POSIX
rules as it may break existing use cases.
Shall we either document that the GNU tee implementation violates
POSIX, or should we go for a change to POSIX to allow this (or is
there already such a discussion)?

Thanks & have a nice day,
Berny