During the past two decades, educating students about sustainability issues has been a concern when designing engineering schools' curricula. One could think that nowadays students are trained to take into account the multiple dimensions of sustainability when addressing a project-based design challenge. Is this really the case? This paper presents an explorative qualitative study on the understanding and perspectives of engineering students regarding sustainability in the framework of such a course. The dataset consists of more than 200 reflexive notes gathered over a period of 3 years. The preliminary results of the study indicate that despite their previous knowledge and training about sustainability, engineering students still have an initial tendency to limit their perspectives and understanding to their own field of study. This points to the need to address the potential bias towards techno-centric perspectives and understanding of sustainability in engineering education by integrating or strengthening additional dimensions, including but not limited to social desirability or economic viability.