probably as a future deterrent, to avoid major conflict - that they are ~~booming~~ becoming more and more formidable opponent and should not be taken lightly.

That's a great question. Who knows what? Who knows who knows what? Who knows who knows who knows what?

That's the game.

So the Chinese know where the planes are. The Americans don't know the Chinese know. The Chinese know the Americans don't know.

The Chinese publish. Now, the Americans know the Chinese know where the planes are and the Chinese know the Americans know.

This is preferrable to believing the Americans don't know if they do know. It changes the behavior of military officers.

It is also preferable for the Americans to know as a deterrent against a first strike.

The big question is, if this advantage is worth it, then what else do the Chinese know that the Americans don't know they know?

Basically they want people to think they're stronger and that the US is weaker. It's a PR campaign. The US almost certainly has had the same capability for a while and simply had no need to advertise.

Recognize that the US would be foolish to fly a stealth fighter/bomber within range where multiple radar could lock on. They'd start their attack campaigns from far out and pick off the known ground radar installations at the perimeter, along with downing aircraft that tried to intercept them. After that, the US would have air superiority and only have to worry about mobile radar units. In any case, once they turn the radar on to look for the planes, they're broadcasting their location and the plane can just launch a missile down their throat.

Posturing and psy-ops. It's likely an inflated figure.