IR: unclear definition of middleCClefPosition?

[pls]

Hey all,

in the Internal Reference it says in 
http://lilypond.org/doc/v2.15/Documentation/internals/tunable-context-properties:

middleCClefPosition (number)
The position of the middle C, as determined only by the clef. This can be 
calculated by looking at clefPosition and clefGlyph.

Shouldn't it rather say:

middleCClefPosition (number)
The position of the middle C, measured in half staff spaces from the center of 
the staff.

Here comes a Scheme snippet:

                    (make-music
                      'SequentialMusic
                      'elements
                      (list (make-music
                              'PropertySet
                              'value
                              "clefs.G"
                              'symbol
                              'clefGlyph)
                            (make-music
                              'PropertySet
                              'value
                              -6
                              'symbol
                              'middleCClefPosition)
                            (make-music
                              'PropertySet
                              'value
                              -2
                              'symbol
                              'clefPosition)
                            (make-music
                              'PropertySet
                              'value
                              0
                              'symbol
                              'clefOctavation)
                            (make-music
                              'ApplyContext
                              'procedure
                              ly:set-middle-C!))))

The position of the clef is two half spaces (-2) below the center of the staff. 
The position of the middle C is 6 half spaces below the center of the staff. I 
looked at various clefs (treble, alto, tenor, bass) and middleCClefposition is 
always determined by the number of half staff spaces from the center of the 
staff. It never refers to the position of the clef. But then I'd say 
middleCClefposition is a misnomer and should rather be called middleCPosition. 
Unfortunately middleCPosition already exists. What's the difference? Am I 
barking up the wrong tree?

hth
patrick