It is a possibility I think. The two ship initial trial model could be for cheaper frigates and destroyers. That's why there are 52C and 54original. Same with 71 and 75 classes. The carriers are too expensive and big to have 2 for trial.
Before anyone mention 16/17. 17 is the first Chinese constructed carrier while 16 is a renovation. So 17 is technically alone in its construction. 003 carrier could also be alone in it being a EMAL carrier that is conventionally powered. Once that is learned, they can build a 004 with nuclear power, then the only variable is the power source (big variable).
This will allow a faster learning curve I think. Once the class they like is found, the dumpling making (if that's even possible for carriers) can start.
I would say China will build it's first nuclear carrier after they test the nuclear engine on the nuclear ice breaker first.
In the past PLAN have always tested the reliable a engine system before the ships that use them got mass produced. The one 051B was busy visiting different countries since it joined PLAN, part of the reason might be it's the biggest and most modern looking ship at that time, but more importantly it tested the steam turbine before it powers the future carriers (long story). The mass production of 054A was also after PLAN tested its power on the 2 054, and the mass production of 052D was after the reliability of domestically produced GT25000 has been proved on the second batch of 052C (and the same but improved engine powers the later 055). And if you pay attention, basically all support ships in PLAN that's similar in size are powered by the same thing... There's a idea in PLAN (or China in general) called 通用船舶平台/Universal Ship Platform, that a proven engine system will power a lot of different ships with the same size (or just put more of them to power bigger ships).
If China decide to only have 1 nuclear powered carrier, obviously they don't need to invest in a universal nuclear engine. That's why France just use the enlarged version of K-15 (which powers their nuc sub) on the only carrier they have. But I believe China is more ambitious than that...
Not only there's gonna be more than a couple of nuc powered carriers, but the future nuc powered cruisers, AOEs, and other large ships can all use that as well. (For a example, 4 of them to power a carrier, 2 to power a cruiser of 25k+ tons, 2 to power a AOE of 50-70k tons... and etc). The ice breaker will be the platform to test the engine, and after it's proven to be reliable, we'll see a burst of different nuc powered ships been built.
Since the news of that ice breaker starts to fly around since 2018, I would say there's still plenty of time before we see the first nuclear powered carrier. And that's why I believe there's going to be a sister ship for 003... Both for training more pilots while gaining more experience using catapult, but also to have enough carrier force for operations before the nuclear engine is ready.
Here's a interesting reading for those that can read Chinese:
