Even if steam cat technology is already ready PLAN never used it at sea and would spend a few years getting rid of troubles that are bound to occur. All large flattops are steam powered except the not yet operational British ones. That didn't prevent USN from going to EMALS in its Ford class. What would be the cost of abandoning that system and going back to steam cats? Three years rebuilding and $2b?I have a theory that if steam catapult technology is already ready they may go with it first because it's a more immediate fit with steam engines, and thus present a lower risk approach than figuring out the electrical systems for an EMALS on a carrier, with plans for a refit in the future.
It may also be that they plan on going with EMALS if their experience building the first carrier or two goes smoothly, but with the option of using a steam catapult as a backup option if things are rough.
Finally, I've though that it's possible that decision making within the PLAN is divided, and POP3 either reports for one side, or reports based on available knowledge that could shift around a bit.
The proper back up for delay in EM cats is using the ski ramp. And the best EM cat is built into the ski ramp because such system needs less space as it needs to provide much less speed to get the aircraft safely away.