The fewer unknowns the better the data and the more accurate the experiment.
In terms of predicting how likely someone is to finish their freshman year of collage having a test where you can increase your score significantly with moderate levels of preparation is not a bad thing. However, the fact you can easily game the test means it is a less accurate indicator of a student’s innate capability. The fact you can retake the test creates yet another sort of bias. etc.
More generally, it's easy to focus on defects in the test, which are irrelevant in a larger contest and subject to change.
In terms of predicting how likely someone is to finish their freshman year of collage having a test where you can increase your score significantly with moderate levels of preparation is not a bad thing. However, the fact you can easily game the test means it is a less accurate indicator of a student’s innate capability. The fact you can retake the test creates yet another sort of bias. etc.
More generally, it's easy to focus on defects in the test, which are irrelevant in a larger contest and subject to change.