Clearing some bench tests does not make an engine successful, Chinese pilots complained of performance issues back in 2007 and even as recently as 2009 Lin Zuoming stated that the WS-10 had quality issues. Regardless of when the WS-10 entered service the production line of both the J-11A and J-10A lasted years beyond their introductory dates.
In total China operates over 200 J-10A's and J-11A's, one has to not only factor in time between overhauls TBO but also engine life and lets not forget that the J-11 uses 2 engines. Both the J-10A and J-11A will remain in service for a long time likely at least a decade.
So again, were Chinese engineers that incompetent and foolish to make the WS-10 incompatible with J-10A's and J-11A's? What is even the point of making the engine incompatible? If they were smart they would make all their engines universal so that when a J-10A's or J-11A's engines are due to be replaced they can replace them with Chinese made ones that are likely cheaper than the imported Al-31 counterparts. Again assuming that what you said is true, the incompetence level at Shenyang is at a fever pitch.