It seems to me that If the 004 carrier is already under construction, then whatever they are doing now to the ground based deck design test facility in Wuhan will be too late to seriously benefit the 004 design. So either 004 is not yet under construction, but still at the relatively mutable, tunable stage of design development process, or 004 is actually under construction, while the Wuhan building is being configured to reflect a substantial design change envisioned for the follow on design to the 004.
if the latter is the case, that strengthens my suspicion that any carrier China is currently building would be similar to 003, possibly a repeat.