The metric used in this article is likely different than the metric that the port operators care about. The article was measuring productivity by turnaround time for ships. The port operator probably cares most about operating costs. Excess turnaround time for ships is a cost born by the shipping line (and consumer), and it is unlikely to affect whether people choose a given port because geographic concerns dominate most.

The goal of the port operator is explicitly to lay off longshoremen so they don't have to pay inflated salaries. It is diametrically opposed to the union's goals in this regard, hence the dispute. The article largely acknowledge that automation succeeds in reducing the number of longshoremen required, which is its actual purpose. (It did question whether the reduced labor costs actually pay for the capital investment required, but didn't give any numbers. Since capital investment is a one-time cost but wages are a recurring cost, this calculation needs to be subjected to discounted cash flow analysis, which also requires that an interest rate be specified.)