I believe the idea is that the entire curriculum is then centered around teaching the test, versus what kids actually need. As to whether that's the primary issue, no idea.
Do you really think reducing standardised tests would improve the education system?
If so, what objective evidence can you provide for this belief?
Your comment is precisely the problem: objective metrics will always support their proponents' arguments for more measurement, while any upsides to a lessened objective grading will be difficult to show because they'll involve subjective assessment or less assessment.
Do not confuse the investigator's convenience in accessing a truth value for the truth value itself.
Edit: she was Assistant Secretary, not Secretary