I believe these aircraft were bought (if in fact all these khafee rumours are true), after 27th Feb 2019. Chinese premier basically offered anything and everything to PM IK. IK didn't just do nothing with it, but asked the three services to go on a spending spree that will create a rearmament that Pak has been lacking since the 1980s.
So, PAF pilots have been training on these platforms and learn, adapting them in China for more than a year now. This is not like the 1980s when a plane could take years to master - at that time, Chinese doctrine was very primitive and thus Pak had do develop doctrine, tactics and operations from scratch.
Proof in this regard can be seen on how quickly the PAF got F-16s operationalized against Afghan and Soviet air forces.
Another issue raised is naval aviation doctrine, some are saying developing this will take a long time. They are ignoring that PAF / PN have been operating Mirages and JF-17s as naval aviation platforms for decades. All that is happening is more capable aircraft are now here, giving them greater range and payload.
Drowning men clutch at straws. Same people that didn't believe these purchases are now making up stories about how adapting to naval aviation will take a long time, how adapting new aircraft will take 8 years or whatever other garbage theories they are spewing. Mature analysis suggest PAF would be able to get new aircraft operationalized as fast as the Rafales, if not faster.