Maybe I didn't make myself clear, I said it is highly unlikely that WS-10B is not compatible with serial J-10, not that it is incompatible
There are couple of things you have to remember:Not sure why You think so !?? ... We have already seen the WS-10A being interchangeable with the AL-31F in a Flanker (see J-15 prototype '554') and I can't think that this is only a specially modified aircraft to test both engines. As such I assume the WS-10B can be used on a standard J-10B with only minor modification and not like You suggest via a completely redesigned internal structure. I can't think that SAC has an AL-31F and WS-10A-structured J-11B on the line and the same also for CAC.
Most likely the WS-10 was designed from the beginning with a possible engine-change in mind ... if that will be done is a different story, but stories that the WS-10 has a marginally wider diameter and won't fit a standard fuselage is non-sense.
IMO the latest AL-31FN series III is simply now a bit more reliable and has a higher thrust than the now available WS-10B and that's the reason for the J-10B still being AL-31FN-powered.
So how many J-10Bs of this 1st batch? and who is going to get them?