You understand that these aren't stealth platforms and that there are radars all over the place in that region, right?

You understand that giving them up to two hours of advance notice lets them do things that they couldn't do in the much shorter amount of time from when these fighters show up on radar? Like moving all of their high-value personnel away from places that they are known to have frequented? Setting up specific anti-aircraft assets in specific locations at that exact time so that they can more effectively engage with an attack that they know is coming - and with which specific weapons platforms, so they can optimize their response?

The reporter never should have been added to the chat. But in terms of the actual information, once they let partners in the region know they're Doing Something the cat is effectively out of the bag.

No, it's not - because those partners in the region treat classified information carefully - knowing that if they don't, they won't be given a heads up in the future. Giving partners in the region a heads up through secure channels, to people who are cleared for that information, is not the same as letting information leak to a third party because the Secretary of Defense didn't have enough sense to avoid typing that specific information into an unsecured commercial app.