True but that can hardly be considered a plus for the Chinese, especially in terms of intellectual property integrity and such. One can say that the act of China producing unlicensed copies of the Su-27 had directly sunk several other potential deals with Russia, like for the Tu-22M and the Ka-50. Both of which would have been great force multipliers for China. Russo-Sino cooperation would have been much more successful.
At least Japan would have little difficulties in building more F-15s if they want to as there is little reason as to why the US would want to block such a move from an ally for a plane that they aren't actively making themselves.
China has said from the get go that the aim was to eventually raise domestic content in the J11 to 100%.
The Russians had no problem with that when they first signed the contracts because they vastly underestimated Chinese capabilities and thought it would take China so long to absorb the tech that once done, it would become obsolete and China would then need to buy the latest Russian Flanker version developed with Chinese money, and thus create a self-sustaining loop where Russia re-capitalised its defence industry with Chinese money.
But China advanced far quicker than Russia expected, not only cancelling the outstanding Su27 kits order, but also stopped Su30 purchases after delays and underwhelming performance of the MK2. There were no mention of broken contacts when all that happened.
Relations didn’t break down until Russia failed to deliver on its Il76 contract to China after repeated assurances and broken promises.
That resulted in China cancelling the whole contract, and Russia tried to turn the screws on China by stopping AL31 sales for sino Flankers to try and get China to reconsider.
As for the Tu22 or Ka50, there was never any real evidence of strong interest in those types from the China side. It was all Russian sources sayin China wanted them.
Chinese defence co-operation with Russia advanced as far and as deep as it could, because no nation would give you their crown jewles tech, just look at the F35 source code spat between the ‘special’ friends US and UK.
Russia would not have transferred core technologies no matter what (just look at how much India is on the hook as far as Russian support for their joint venture systems). That’s just the reality of the game.
As for Japan making more Eagles, that’s easier said than done seeing how the production line has been closed for decades in Japan. Are the tooling and machinery still even viable even if they have not already been scrapped? And there is also the bigger problem of skilled workers needed to run the line even if the machines are still in working order.