I am not sure whether the Quebrada de Humahuaca including Tilcara and Coctaca are within the nominated area.
Agreed - they are NOT included in the Qapac Nan inscription.
The Qapac Nan nomination file is very long and complex and, whilst including sections on the entire Qapac Nan, doesn't permit easy identification of which smaller parts of the whole are actually included. So the Qebrada de Humahuaca gets exposure for having a major section of the Qapac but a detailed reading of the maps makes it clear that the (relatively) nearby inscribed section is NOT a part of the Quebrada inscription.
The relevant segment of Qapac Nan is "Quebrada Grande - Las Escaleras Code: AR-QGE-01/C-2011."
This is the only segment situated in the province of Jujuy in which the Quebrada de Humahuaca is also totally situated.
The map provided for the Quebrada inscription isn't very good but shows a "greyed" inscribed area following a generally N-S direction shared with Route 9. The relevant area for assessing any possible overlap with the Qapac Nan inscription is that between the towns of Humahuaca and Huacalera. Google Maps shows these to be 29 kms apart.
The relevant map in the Qapac Nan nomination is on page 1922 of the Adobe Nomination document. It shows quite clearly that the nominated segment of the Qapac Nan is situated SE of Humahuaca and SE of a town named "Santa Ana" and very close to the border of Salta province to the east. This section is a relatively short stretch of "road" (see map on page 1929)
Google Maps shows Santa Ana (AKA Valle Grande) unconnected by direct road (according to Google) to Humahuaca approx the same straight line distance from Humahuaca as is Huacalera. This must place it outside the "grey" inscribed area of the Quebrada map since a 29km circle from Humahuaca goes well beyond any area inscribed to the SE of Humahuaca. This is also supported by the smaller scale Qapac Nan map on page 1921 map which shows Santa Ana to be in a different valley from that of the Quebrada which follows the main N-S valley -with, I suspect, its watershed as the boundary.
It is also perhaps worth noting that the section of the Qapac Nan nomination which describes sections already under protection of some sort refers to the "Biosphere Reserve Yungas (Declared by UNESCO in 2002 within the framework of the MaB Programme"
and not to any WHS inscription for this segment.
PS. I have just looked up Valle Grande and got this web site http://www.argentinaturismo.com.ar/vallegrande/
It refers to "La posibilidad de llegar hasta la Quebrada de Humahuaca en una emocionante travesía;"
which clearly supports the conclusion that Quebrada de Humahuaca is separate from Valle Grande and "over" the mountains - albeit not that far!