Well a few observations that we assume to be true and carry certain insights.
1. No J-10s have been seen outside CAC production facilities in months.
2. Guizhou Aircraft promotion material once indicated J-10 production will shift from CAC to GAC while CAC presumably focuses on making J-20s (now estimated to be upwards of 80 per year BEFORE new facilities are even accounted). This means in future, J-20 production should easily be more than 100 per year just from one production facility.
3. GAC has not produced any J-10s shown outside their facilities and PAF's J-10s have come from CAC.
4. PAF allegedly has bought more J-10 than the initial order of 36.
5. PLAAF is embarking on newer generations of fighters and platforms. Taking resources away from buying more 4.5 gen fighters.
6. SAC can build more than 60 J-16 plus a few dozen J-15 per year but current estimates put it at those numbers. They may be involved with 6th gen like CAC or in competition. Certainly SAC has UCAV programs too that are different from the several flying wing UCAVs that are either in service or flying prototypes that have lost out in competition with those that are not disclosed (won competition and used for service).
What do these suggest?
1. China considers J-10s something it is growing out of. Its usefulness is limited by size, payload, range. But it is far more affordable than a 4.5 gen equivalent option of J-16. Still the J-16 can fight much further away whereas J-10 flying those missions require much more planning with tankers support. J-10 is therefore a defensive regional fighter that must be placed nearby potential conflict zones. This is of course not a matter for PAF since the relative size of the airspace that require guarding for PAF is suitable for J-10.
2. With China's 6th gen platforms progressing (also to meet the threat of US inducting 6th gens in those timeframes), more resources are required in that direction. Buying more J-10 just doesn't make much sense. A similar level of sensor technology and payloads can be done by larger UCAVs for cheaper than making a J-10 and training and supporting a pilot. We have seen at least three different types of flying wing larger UCAVs from China that are at least flying even if two of those three are supposedly the ones that lost procurement competition or have not been involved in competition (not true reason surely since branch of AVIC wouldn't do such a thing for no reason therefore only reason for show is either leak of in service UCAVs captured by citizens when it flew by or less sensitive due to not being selected for service).
3. China needs long range fighters and heavy ones to carry the equipment and sensors necessary for longer range engagements and directing various types of drones. J-10 is a good supporting regional light weight fighter but in this role it is limited.
4. Pakistan allegedly wants to buy many more dozens of J-10.
5. Where would Pakistan get these if CAC is no longer producing them? Is there a hope that China has transferred J-10 manufacturing and line to Pakistan entirely? If so, where would Pakistan have possibly gotten the money for not just that but also setting it all up. Would China allow it and trust it since it has roughly 500 J-10s in service and will not be retiring them until late 2030s at the earliest.
I think Pakistan is just buying the 36. The rest is either intentional misleading talk or other sort of deal was agreed by both nations. J-10 while less important than J-16 strategically, it is still such a fighter for PLAAF that if details and information get into Indian or American hands, it does present as security issue even if slighter than J-16 details. Therefore production transfer is less believable. I think China genuinely feels 500 J-10s is enough and resources for more 5th gens and newer platforms are more important. GAC will make it in future (or now) for newer customers as CAC hands over production to GAC. Pakistan being the first customer means the first few batches were made before in CAC and working with GAC for future batches perhaps? Since it's produced in a different facility and China may have stopped inducting J-10s earlier this year, it is simply how these things aligned which make it appear PAF J-10s are coming from the ether. The first batches were made by CAC a while ago and newer ones may be from GAC.