I seriously doubt the second interpretation is realistic. The PLA and the Chinese government in general are well aware of China's deteriorating security environment and the range of threats it faces. It would indeed by astonishing (and horrifying) if Chinese decisionmakers were so monstrously negligent as to ignore these threats, but I just can't see that being the case. I discount scenario 2 completely.
As for scenario 1, China didn't establish a naval nuclear propulsion industry last week. It's had one for decades and has been researching nuclear propulsion for aircraft carriers for a very long time. I've always felt that people put these completely silly and arbitrary "requirements" on China's nuclear propulsion research, like the thing with installing a nuclear reactor on an icebreaker. What other country did that? Did the US do anything like that? If not, why should China be expected to?
The reason for this bias and consistent underestimation of China (even among its supporters) is, of course, obvious: China was lagging behind technologically until very recently. Note the tense, however - was. In all but a sliver of fields, China is at the very least competitive. It should come as no surprise that that sliver is shrinking day by day.
Some projects have been pleasant surprises, some projects have been disappointments. All of those pleasant surprises and disappointments however have been tracked with occasional updates of rumours and/or information on how a given project is progressing.
In the case of this rumour that the fourth carrier will be nuclear, we do not have any basis of information to project when it could emerge and pop3 has not given us any indication of it either.
There are persuasive arguments in either direction.
For scenario 1: if the CVN does start construction in the next few years, it could be a reflection that Chinese nuclear propulsion technology is sufficiently advanced and mature for their fourth carrier to use it, and could enter service before the late 2020s.
For scenario 2: perhaps not only is Chinese nuclear propulsion technology less advanced than we believe, but perhaps the strategic environment of the mid to late 2020s is assessed as being so severe, and that pursuing a fourth 003 pattern carrier would not be the best decision to hedge against conflict (i.e.: that more mature and more distributed assets may be more valuable for that time period, versus an additional 003 carrier, as a fleet of four carriers of CV-16, CV-17 and two 003 CVs would be deemed an insufficiently capable force to deal with threats of that time period).
Without a clear indication from pop3 or others, we simply don't have a concrete foundation to make informed speculation in either direction.
That means at this stage, we should remain cautious, and to not write cheques that we may be unable to cash.
So yes -- the idea of the fourth carrier being a CVN is absolutely indeed astonishing.
But we do not yet know what reason it is astonishing, and we should not be presumptive and superlative in our predictions without sufficient basis for it.
The idea of China starting construction of a CVN in the next few years is not beyond the realm of possibility -- but it would be surprising, and we need rumours to seriously entertain it, given how soon that will be creeping on us.
Similarly, the idea of China not building a fourth carrier until the late 2020s (when the CVN could otherwise conceivably start construction) is not beyond the realm of possibility either -- but to confirm it we would either need rumours or to wait until we've reached 2025 at which point scenario 1 can either be confirmed or ruled out.
