I read the links, and the answers are still unsatisfactory.

Here is the abstract from the original paper: https://journals.sagepub.com/doi/abs/10.2466/pms.1989.69.1.2...

> The purpose of this research was to assess how well success in early combat training was predicted by scores on a test of general intelligence

It seems this research pertains to early combat training and not broad, post-training success in one's military career. Not to mention the research is essentially predicting test performance from test performance. I imagine the same predictions can be made about one's two-mile run and one's three-mile run.

> Analysis indicated that intelligence test scores AND run time significantly predicted success, each adding to the prediction provided by the other.

Which is not surprising. It shows that intelligence is just one of the multiple contributing factors. Being exceptionally tall is essential in the NBA, but being exceptionally tall, alone, is insufficient to make it to the NBA.