What would be the " continuous adjustment of the owner's plan in the early stage of the project"? Initial plans called for different type of powerplant?
A major change like that once construction is underway is very unlikely. It is much more likely that they are referring to hundreds or thousands of minor design changes associated with a large, complex new design where the designers are (hopefully!) receiving continuous feedback from the crew of 17
Shandong. If there was a larger gap between carriers then more of those lessons could've been realised and incorporated in the design of 003 before commencing construction, or alternatively they could've frozen the design of 003 without those lessons of experience. If they are choosing to learn on the run and make changes up to the last possible moment it is evidently because they want both for the carrier to be commissioned sooner rather than later, and to reflect (to the extent possible) the current levels of acquired knowledge. And of course the same dynamics and considerations will apply to future carriers as well, particularly for systems that are new to 003 such as the catapults.
I recall a conversation on the Key Publishing forums some years ago, after
Liaoning entered service but before it was known that
Shandong was under construction (and derived from
Liaoning). The poster suggested that China would (or should) have only three carriers by 2030 because going any faster would not allow enough time for all lessons to be learnt from building and operating the previous carrier before finalising the design of the next one. And I think that was a reasonable argument so far as it went. If this were purely a research project that would undoubtedly be the way to do it. What the argument neglected was the strategic case for a greater level of in-service capability in the 2020s and 2030s.