Even as someone who approves of your sober approach over nationalist frenzy, I think it is too much to ask people not to celebrate raucously at such a huge milestone. Symbolically taking the lead in global fighter aircraft (even if the truth is far more nuanced) is the biggest breakthrough in PLAAF history.
I beg you all to be patient and even more rationale!
As much as I admire China's progress and you all surely know me, how much - sometimes over- excited I am, I beg you to calm down a bit: Is China indeed "taking the lead in global fighter aircraft"?
Surely if they will show the J-XD-demonstrator soon it is a major "breakthrough in PLAAF history", but we all know, that the USAF already has similar "demonstrators" flying since years! They only did not unveil them to the public yet.
Again, I do not want to downrate this "breakthrough", but to immedealtly jump the bandwaggon and call it "China is leading" is IMO too early ... As such you are correct with your second part: It is surely "Symbolically taking the lead in global fighter aircraft" development but to make a conclusion we simply do not know enough!
... even more so, it hasn't been unveiled yet.