Typhlix
The MC doesn't remain stupid he starts to do things smarter in later chapters. The Author introduced the MC as an idiot muscle-brain who says he won't think because it hurts. The author later explains, in later chapters, that the MC really does feel real pain when trying to think about things. This is due to the fact that something changed in his new body when he transmigrated into this world and his brain works far to strongly for his cultivation level and his current body doesn't seem to be able to handle it. As we get into later chapters he starts to be less stupid and does things with a bit more thought. It seems to have gotten much better than the start of the LN. I've read up to chapter 307 so far.
The institutes approach seems very dumb. First of all they won't get an accurate reading of the time and second of all it's way too dangerous if the student was mistaken. It's sheer impossible for any student to get tested within 1 hour. Because the introduction and the walk to the test station alone takes longer than that. Especially if they sleep x hours before getting tested. The smartest and most logical approach would be to let the transplanted microchip AI do the job. The microchip could send out certain weak impulses (pain, pleasure, whatever) and measure the hosts bodys reaction and/or brain waves. As soon as the 100x sensority increase vanishes the AI chip would know immediately and could record the exact timing. I can't imagine they having such advanced technology but using such backwards, dumb and inaccurate approaches.