Centrist orthodoxy is far different than Modox. I doubt Rav Aharon would call himself “Modern”
There is not such thing as “centrist orthodoxy.”
Modern Orthodoxy refers to the hashkafa of Yeshiva University (sometimes called “torah umadda”). To my understanding it is mainly distinguishable from other orthodoxy in its acceptance of secular knowledge as a proper goal in itself, and in its willingness to look to the secular world and integrate the good of the “greeks” into the torah.
For further readings, see Torah Umadda by Norman Lamm; Leaves of Faith by Rav Aharon Lichtenstien (rosh yeshiva of Gush, and son in law of Rav JB Soloveitchik).