They're saying that it won't break because that's not the purpose here. The description of the experiment is:
In addition to safely integrating into the Microgravity Science Glovebox (MSG), the 3D Print requirements include the production of a 3D multi-layer object(s) that generate data (operational parameters, dimensional control, mechanical properties) to enhance understanding of the 3D printing process in space. Thus, some of the prints were selected to provide information on the tensile, flexure, compressional, and torque strength of the printed materials and objects. Coupons to demonstrate tensile, flexure, and compressional strength were chosen from the American Society for Testing and Materials (ASTM) standards. Multiple copies of these coupons are planned for printing to obtain knowledge of strength variance and the implications of feedstock age. Each printed part is compared to a duplicate part printed on Earth. These parts are compared in dimensions, layer thickness, layer adhesion, relative strength, and relative flexibility. Data obtained in the comparison of Earth- and space-based printing are used to refine Earth-based 3D printing technologies for terrestrial and space-based applications.
The description is not "Print out a wrench so that crew members can change a rusty lug bolt". And yes, also from the description page, they include direct metal printing as part of their list of ultimate goals with 3d printing in space research.