(a) The purposes of this chapter are--
(1) to encourage noncareer service in the uniformed services by
eliminating or minimizing the disadvantages to civilian careers and
employment which can result from such service;
(2) to minimize the disruption to the lives of persons
performing service in the uniformed services as well as to their
employers, their fellow employees, and their communities, by
providing for the prompt reemployment of such persons upon their
completion of such service; and
(3) to prohibit discrimination against persons because of their
service in the uniformed services.

(b) It is the sense of Congress that the Federal Government should
be a model employer in carrying out the provisions of this chapter.
That's the 1974 language used in the implementing document to add the Act to the US Code. Recall that in '74, we were transitioning from a draftee to a "volunteer" force. Many of the provisions have been changed (generally, expanding 'qualified' service)... as recently as 2003.

My understanding of the use of "Affirmative Action" in this law, is so the Human Resource guys could bundle their "how we comply" plan in one catch-all package, to show the Dept o/Labor guys "Here is how we don't discriminate against race, gender, religion, military service, etc. etc.".

But, I'm not sure I answered your question. Do you challenge veteran/disabled-veteran preference in hiring/contracting?