There are not other military officers here, so I likely know more than all of you. I likely know more than the person who wrote the article.
First, military officers have zero obligation to show loyalty to a president. Unlike the monarchies or grand socialist empires of the last century, US military officers take an oath to the constitution. Not a person or a party. In fact an officer would be obligated to crush a president who was a threat to the constitution, or violate their oath of office.
Second, the assertion that Milley did something he shouldn't have assumes that China has been declared a hostile force (like ISIS). They have not. So notifying Xi Jinping of an imminent nuclear attack launched by by an off-kilter, Greg Stillson-like president would be no different than notifying Macron, Johnson, or Merkel. Which few outside of the strict Trump circles would regard as even remotely treasonous.
Ultimately it will be up to Biden to decide whether he wants a guy who favors what he sees as doing the right thing over someone who favors loyalty uber alles.
If I were Biden, I'd tell Milley to put a bullet in my ------- brain if I ever acted even remotely Trumpian. It would be an order.