Obama has governed as a moderate conservative—essentially as what used to be called a liberal Republican before all such people disappeared from the GOP. He has been conservative to exactly the same degree that Richard Nixon basically governed as a moderate liberal, something no conservative would deny today.
I would dismiss this as yet another attempt to recast a former president as centrist in the eyes of history. Almost every former president could be called centrist if you cherry pick. But this is a well written article and worth reading.