The Maunakea Spectroscopic Explorer (MSE) is the project to transform the Canada-France-Hawaii Telescope into an 11.25-m aperture telescope, dedicated to highly multiplexed, visible to near-IR spectroscopic studies with multiple spectral resolution modes. MSE successfully passed Conceptual Design Review early in 2018. However, the baseline architecture presented at the time did not perfectly meet the science sensitivity requirements over the entire spectral range. Before entering Preliminary Design Phase, the Project Office then created a science questionnaire for the science team to ascertain their precise needs in terms of sensitivity, multiplexing, and spectral resolution based on the updated science cases. This paper will focus on the process followed by the Project Office to define the appropriate questions, process the answers, and propose a revision of the high-level science requirements for the spectrograph's designs as part of several trade-off study analyses derived from the questionnaire. The impact on both the spectrograph designs and the whole system will be discussed.