The given statement is true.
Some of the health science sites may restrict employees from wearing perfumes or other fragrances because the chemicals in the fragrances can stimulate reactions ranging from headaches to palpitations of heart in some of the individuals who are sensitive to them, making it tough for them to work efficiently.
With time, the individuals getting exposed to the chemicals present in the fragrances become more sensitized to them to the point that they can no longer tolerate any more exposure. This can initiate breathing issues, nausea, sneezing, disorientation, and in extreme situations, they can even go into shock.
You could have made sure the books were the same weight and your friends could have done it at the same time as you