I feel like PLAAF would want boom refueling eventually though. F-35 has both I believe
There is neither a logical explanation nor reason for expectation to shift their Aerial Refueling Infrastructure to a 'not-so-efficient' Flying Boom system. F-35A uses it because the main operator and contractor for F-35A is the USAF.
USAF Air Refueling Assets largely consist of Boom due to their strategic assets such as Bombers, Transport Aircrafts and Maritime Patrol Aircrafts (MPA) and at this point it became more of a tradition for USAF. In practice, when it comes to large aircrafts such as these, Boom is quite useful but it's not so efficient when it comes to refueling some Fighters such as F-15, F-16 & F-35A and prone to cause partial damage due to the location of the refueling port on such small aircrafts.
F-35B & F-35C are using Drogue-Probe method due to its' requirement of less of a space, it's less prone to damage the leeching aircraft and more flexible when it comes to long range flight missions. Furthermore, the Allied Forces such as France and UK to field probe-drogue which makes it even more desirable for USN & USMC due to the nature of their overseas deployment.
So no, J-20 shall stick with the current method for the time being until a new method surfaces. Can't speak for the 'yet-to-be-seen' Stealth Bombers of PLAAF though.