Here is a previous thread: MIDI Octave and Note Numbering Standard

My understanding is MIDI specifications do not mention any octave number for middle C because there is not good agreement on which octave number to use. But my understanding is that MIDI specifications are otherwise clear that:

MIDI note number 60 is middle C.
MIDI note number 69 is A 440 hertz.
MIDI devices use 12-tone equal temperament by default unless other kinds of tuning messages change that.

I think it is well known that there is no universal agreement about what octave number to use for middle C. Anyone who is specifying pitches using pitch letters and octave numbers should explain what they consider middle C to be to avoid confusion. (Or provide the frequency of some note in hertz.)

@Bavi H, thank you for your reply AND for providing a link to the six year old discussion regarding my question.

The linked discussion rather concisely displays nearly every pro and con viewpoint possible about (1) should an octave designation be attached to the "note 60 equals middle C" specification and (2) if so there are at least two standards that define middle C, which standard should be used? 

What the much earlier thread does not touch upon is why the midi middle C standard needs the addition of an octave number.  The most reasonable reason I can give is the general population has a renewed interest in midi with the continual release of MIDI 2.0 standards.  Once again midi is exciting!  The best way to kill excitement is inconsistency.  Midi 2.0 has the opportunity to eliminate much of the inconsistency.  But how is that possible you may ask, it's a two step process.

Step 1 is to assign an octave value to middle C equals note 60.  Of course to assign an octave value the specification also has to state which standard the octave value is derived from.  That way there is a starting point for everyone to understand where middle C resides within an instrument's range.

Step 2 is during a midi device identity interrogation the midi device middle C octave value is returned.  Midi 1 hardware devices can be assigned a middle C octave value from either a look up table that will be compiled over time or by a one time user setting.

While it is well known (by many musicians that frequently use midi) that middle C has no octave assignment the same may not be true for beginners.

Perhaps with Midi 2 renewing interest in midi now is a good time to revisit the question.