? does the Advisory Council on Historic Preservation (ACHP) trump the Mayor's Agent ?

The HPO report on the most recent revised McMillan master plan mentions the "Advisory Council on Historic Preservation."
   
Here is the brief mention of the preservation covenant in the latest HPO McMillan report:               
 
 Preservation Covenant 

In 1987, as a condition of transfer to the District of Columbia from the General Services Administration (GSA) and prior to its local and National Register listing, a preservation covenant was attached to the property. The covenant required that rehabilitation and renovation work be undertaken in accordance with the Secretary of the Interior’s Standards for Rehabilitation and that the project be reviewed by the Historic Preservation Officer (SHPO). The covenant states that if the SHPO did not “agree with” the plans (legally imprecise language that presumably means that they are found not to meet the Secretary’s Standards), the District would request the comments of the Advisory Council on Historic Preservation in accordance with 36 CFR Part 800.
             

As the project will result in substantial demolition of character-defining features and the redevelopment will compromise the open-space quality of the site, the SHPO concludes that the project does not meet the Secretary of the Interior’s Standards for Rehabilitation and Guidelines for Rehabilitating Historic Buildings and advises the District to forward the plans to the Advisory Council for comment.

So what is the Advisory Council on Historic Preservation? 
                          
Here is the website. 

     

Here is the tagline from the ACHP website: "The Advisory Council on Historic Preservation promotes the preservation, enhancement, and sustainable use of our nation’s diverse historic resources, and advises the President and the Congress on national historic preservation policy."
                                                                                               
I recall that an attorney from ACHP testified at a McMillan HPRB hearing earlier this year.  I can't recall her name, but she spoke about the preservation covenant in her testimony
      
And as far as I know, the McMillan preservation covenant hasn't been mentioned since then.
         
Could the Advisory Council stop the McMillan project dead in its tracks? I have no clue.   

Does the McMillan project get forwarded to the Mayor's Agent before or after the project gets forwarded to the Advisory Council on Historic Preservation? 

Do the opinions and decisions made by the Advisory Council trump what the Mayor's Agent may decide? Hoping that someone can provide some clarifying info.

One might anticipate that Holland & Knight partner attorney Carolyn Brown will be present at any possible hearing(s) on McMillan before the Advisory Council on Historic Preservation.