Are you sure about that?
What constitutes being part of the administration?
Thanks for your answer, but it needs a little more to go with it. The members of that board are selected by and report to the Under Secretary of Defense, not the President.
Let me be sure I understand your question. Are you asking if a group of advisors who are appointed by and serve at the pleasure of the administration (I always assumed the SECDEF but perhaps it is the USECDEF), who appear on the Department's organizational chart, whose meetings are published in the Federal Register, etc., etc. are members of the Administration? IMHO, the answer is yes.
I'm too busy to research this but if you'd like to and find I'm mistaken, please let me know.