I think they should use this kind of testing in order to find flaws in the system. It would be nice to know what parts need more funding and other that need less care. The country is not going to balance this by avoiding the issue,but these tests will help.
If this test was administered to all students in the country students in the different regions of the country would score differently. This is because in different regions of the country students are taught at different paces and some get a better education than some. Students in the South East would have a different score than students in California.
A uniformly applied test assumes that students are capable of learning and progressing in a uniform manner when they clearly are not. Students progress at difference paces - some much faster and some much slower - which requires the skills of an experienced educator to be able to tune their classrooms to fix. Suddenly dropping a standardized test to examine all of them to see "progress" only shows a snapshot of that moment - not how much work and progress is being made.
No, a standard curriculum-based sample test should not be used to determine how students from different regions of the country are progressing, because it would be comparing apples to oranges. Curriculums are never exactly the same in one school to another. It would be too hard to compare one school to another in a fair way.