When the US was developing stealth technology, they hid it as well as they could. The F-117 was fully operational in 1983 but the world was only told about it five years later; in those five years who knows what damage could have been done by a fleet of ‘invisible’ bombers?
Now China may have a basic stealth plane, but they’ve announced it publicly at the prototype stage. And they’ve let people see how the control surfaces and everything work, which means that any major power (read: the US) will be able to model it and find out just how invisible it is. Looking at the size and movement of the tail fins, I can’t imagine that it’ll be much of a competitor for the F-117, let alone the F-22.
There’s obviously a place in international relations for letting others know that you have an amazing, invisible attack option; hence the B2 being one of the most recognisable aircraft out there. But nobody really knew what the details of the B2 looked like until well after it was operational. Letting people know that you have a bare-bones low observability plane, and showing them close ups of what the major parts look like, seems to neutralise any real threat it might pose.
Unless it’s just an ego project, and the Chinese just want to be able to say “we have a stealth plane”, rather than be able to do anything with it. Which is entirely possible, I suppose.