well, there really is. I think from the Chinese perspective, they are not violating the agreement, because they have a different view of IP than Russians. They are certainly not exporting J-11B, that was all nonsense made up by the Russians to appear sympathetic.
I do not recall seeing any J-11B's shown at the 60th anniversary, could be wrong there because the commentator probably didn't make a distinction between J-11 and J-11B. But from the Russian point of view, the J-11B is a violation of the contract. Now, it may be a matter of interpretation, and perhaps the Chinese are correct, but my point is that is isn't in their interest to anger the Russians. That is why the J-11B is so mysterious; they are trying to keep it low key because they know the Russian's think it is a violation of their property rights. What is to stop Russia from halting AL-31F/N shipments in retaliation for a plane that they do not want in production?
Seriously, how many high quality photos do we have of the J-10B compared to the J-11B, even though the J-11B is in far greater numbers and has been around since 2006. The J-11B is being kept in the closet by comparison.