For the original commenter to be wrong you'd have to argue that they've been underutilizing what's possible in the state of the art. Looking at the Wikipedia page, I don't get that impression. It sounds like giant engines and equipment on the terminal side are the main limitations, and I assume those capabilities have increased over time. Maybe the original commenter is wrong, although I highly doubt that cargo technology has been underutilized unless the cost of state of the art is/was truly so astronomical such that it genuinely doesn't make financial sense.
With crude oil tankers decades ago the indicators were the bigger the better financially, so that's what was done, and bigger ships were built and financial gains realized.
It was only proven how big was too big once a few ultra-large had been built, and the point of diminishing returns had been exceeded enough so accurate math could finally be accomplished.
Routine commercial operation has been scaled back decades ago to less than the max.
Less than the max that is physically possible, focused now more accurately on better returns.
