It's not that strange; most of the photos and videos of PLA in service airframes, tend to be centered around a few moments (e.g.: the September parade/workup, or maybe videos of a major exercise or something), rather than giving us true continuous up to date production.
If past J-20 production and service tracking is anything to go by, we may go a year or more without confirmation of new airframes, and then in a spurt get a few new airframes indicative of a new unit, and then nothing for another 6-12 months, and then rinse and repeat -- and all of course in a non-representative sample in a manner that doesn't allow us to really extrapolate anything that is up to time.