I suspect that efficiency does not weigh too heavily in the PLAN's quest for developing their carrier operations. If we consider that STOBAR operations will at best offer marginal capabilities when compared to full CATOBAR. Then they rebuilt 001 to see how a sizable carrier is put together, and then built 002 just to see if they could build one from the ground up. With the 003 being a clear step ahead from the previous two carriers, maybe building and operating those is one big training exercise at a military industrial scale!?! Maybe this is the most efficient way the Chinese have mapped out towards developing a carrier capability. But if nothing else, it's plenty impressive in any case.
Of course, as
@ngatimozart so poetically illustrated above, until the chips are down and you're actually at sea operating in real world conditions it's largely an academic exercise. But I think we can assume the Chinese are more than capable of obtaining things like training manuals for CATOBAR operations. And it wouldn't surprise me if they had people infiltrate the US and/or French navies to experience working on a carrier, or maybe even bribe or turn some people to gain access to more knowledge and experience.
In the end I don't think that STOBAR is the goal of the PLAN but something more like an intermediary step. And it wouldn't surprise me if they got rid of these ships at some time in the 30's.