Since the carrier is likely to outlast the planes by factor of 2 or 3, shouldn't it be the aircraft design that fits the carrier, not the carrier design that fit the aircraft?
Well it is pretty clear that the J-15 is being heavily invested in and is intended to be their carrier strike fighter of choice.
There is currently nothing on the near term event horizon that suggested any change away from that.
My guess is, that the J-31...still in protype phase...is at least 7+ years away from any full production decision. Even then, if it was ever considered to be a carrier aircraft, it would most probably have been desinged to be able to operate off of the Liaoning STOBAR design.
So, two indegenous carriers with a similar STOBAR design to the Liaoning makes a lot of sense, and will be able to operate both of the PLAN's carrier capable aircraft, and particularly the J-15 which is what they are just starting to produce.
These carriers will save the PLAN a lot of money in terms of logistics and training with respect to their existing Liaoning. They will give them very ample time to consider and then design the next phase of their carrier ambitions/plans with an indegenous CATOBAR design which they then may build at least two of, starting sometime in the next 5-8 years.
This would give them a total of five carriers (which I believe the max number they will be looking for), the last of which is launched a good 12+ years from now and put in service in say, 14 years....2028 time frame
From that, outside of the engineering spaces, they make a similar design for their nuclear carrier (if they decide they need it) and that becomes the class they put inservice to ultimately replace the three STOBAR carriers we are speaking of now. But that does not start happening for 30 years.