It has to do with the combat space taken comprehensively (the intent of the integrated command space).
In the naval domain, the A&N islands role for example as its a massive asset, a very large but fixed bunch of aircraft carriers in a prime location. What will its role be, how can be further leveraged here while the overall wherewithal lags the main opponent.
What are the things that will have to be worked upon with allied nations, what roles are they willing to play in the various tiers of conflict concerning us.
Then yes, exactly things like what you have described with the actual final production of war assets and training of their crew and research into improving all of these (sensoring and weapons especially, either hosted by the naval mobile assets themselves or stationed on land, air assets, space etc that will play a more effective role in the naval domain with more integration).
i.e If MDL, GRSE et al have (or soon will have) X shipyard berths and capacities at hand that are now larger than Y of yesteryear that allow say a 4+4 economy of scale compared to 3+3. Or is an 8 at one go even possible? i.e is there a significant chokepoint in this layer....along with considerations of capacity for building other (especially smaller) ships and tradeoff studies here for their numbers required (in that comprehensive combat space reality and projection regarding frigates, corvettes, subs and so on).
I have simply not looked at the shipyards themselves regarding this potential. I would assume 4+4 is the natural transition from 3+3 though.
Then the next layer is very much the maturity + confidence invested in the system from operation of preceding blocs and their subsystems reliance etc.
i.e assuming for sake of argument all 8 production slots open and available, do you commit all 8? Or commit 4 (and wait and see w.r.t operations and tech developments) and commit the next 4 later (to take advantage of what was developed in the interim and also having 4 production slots available for other warships that may be more appropriate for the force level ramping strategy picked), very much like you have described.
There was only some fairly nominal upgrades between the Kolkata and Vizag classes from what I have looked at (compared to their total costings)....so maybe these indicate more cohesion in the successor class for all 8. Or maybe the raw tonnage increase and all other considerations are the imperative default and a 4+4 conservative approach (essentially scaling 3+3) is preferable even with 8 slots.
If the shipyard berths are constrained to 4+4 anyway (i.e thats the chokepoint), its moot point largely as at that point you want the next 4 to take advantage of the time they were unable to be produced earlier.