Exactly. Just take the very example you gave. Its a mess. Its easier to manufacture one different VLS than three, so you not only are saving space, you can be potentially saving money in manufacturing costs. You only need to maintain one VLS rather than learn how to deal with three. The Nakhimov is more of a mess earlier, at least Redut is trying to replace Gauntlets and Gekko, hard to see why you would need two kinds of point defense SAMs. When you are dealing with a single or two blocks of the same VLS, its probably cleaner and more space efficient inside than the complexity of two or three different sized VLS. On top of that, the various legacy VLS used by that ship are full of round designs that are less space efficient. Building around these designs will also result in less stealthy designs. Look at the round features built for the Osa launchers.I think you misunderstood what I said. I totally understand the advantages of large diameter VLS just as their disadvantages. But this is not the debate. Neither Am I looking on a global scale but rather a ship per ship comparaison.
The russian Admiral Nakhimov is being modernised with three different VLS; Fort-FM, Redut and UKSK. Three systems when only one can do the same job, like the Mk-41 or the Type 052D's VLS. hypothetically, if those systems where comparable in dimensions, the only advantage of the universal VLS would be less space wasted. At least that's my answer to the problem.