As I said earlier- at least they don't push that through the Tsushima Straits as there would be South Korea, Japan, US and later on Russians to keep it down. It's so unrealistic scenario that as I wrote earlier - they could do that in other parts of the world with a much bigger chanses of success. It's so stupid that there couldn't be any meaningful training aside from mobilising 7th Fleet and JMSDF to watch it. And they did with a force of at least 3 Arleigh Burkes with at least 2 additional JMSDF vessels. A force that would be hardly breakable in case of war for entire PLA forces combined.
Are you suggesting that it's not in the Chinese Navy's interests to conduct maritime exercises in potentially contested or crowded waters because of the risk of the ships of naval ships from other nations listening in and tracking the exercise?
The risk of being eavesdropped on and observed by a potential foe is a risk everywhere when exercises are done outside of one's own borders, and the risks of being eavesdropped on must be weighed against the benefits of such an exercise and the experience gained from it. Considering the stage of development of the Chinese Navy and the trajectory its surface forces will likely take in coming years, I think it makes a great deal of sense to start conducting these sort of exercises in the region to not only normalize their presence before more ships and bigger ships start entering service, but also to gain more experience for the officers and sailors so they can hit the ground running as their new ships enter the fleet.
After all, this particular exercise (which tbh for the Navy is one of the smaller ones that they've done) had only a couple of destroyers and a refuelling ship and a dozen or so aircraft, but in a few years it'll probably regularly involve larger numbers of surface warships like a surface action group and eventually carrier battle groups, and involving larger numbers of more advanced naval aviation aircraft and probably with air force participation as well, and increasing involvement from rocket forces and strategic support force.
But to reach those higher levels of sophistication they have to start relatively small -- and this exercise that we are talking about isn't exactly coming out of the blue either, it has been preceded by years of other exercises of varying levels of sophistication.
In other words, this exercise is merely an intermediary stage that must be done on the way to an eventual desired level of capability to be attained in the future.