It is almost certainly the case that the recommendations were made on the basis of obtaining adequate shadow detail, *not* "better contrast." What does "better contrast" mean? More contrast? Less contrast? It depends on the brightness range of the scene you're photographing, combined with your artistic vision.(posted 8690 days ago)A lab, unless instructed otherwise, should be developing for normal contrast. Increasing development increases contrast. Since the recommendation was about shadow detail rather than contrast, the lab should not be instructed to alter development.
The statement that improper development would result in overexposed images indicates a lack of awareness about the role of exposure and development on shadow detail and contrast. Adams' "The Negative" is the usual recommendation for learning about these topics.
Ideally, you would test your films in your personal equipment and with your development procedure (see "The Negative") rather than relying on someone else's results.