The government wouldn't be deciding the appropriate curriculum. They would be creating a measuring stick to compare curricula. If, as you suggest, advanced courses were not on it, then it would simply be useless at the top: 80'th and 99'th percentile students would have the same score.

As for colleges cutting advanced classes, I just can't see it happening (1). If they can find students willing to take it, someone will teach topology (it's better than doing Calc 2 again).

Colleges don't suffer from the same institutional failings as public schools (they have their own unique institutional failings).

(1) Note: I have a few years of experience teaching in college, and a few more working in college math depts.

Your view of how this works wouldn't be all bad.

However, the original article was talking about standardized testing modeled after the test used in primary and secondary schools. This includes the government setting minimal, uniform standards, and has often led to cutting "advanced" or "peripheral" material to concentrate on teaching "fundamentals" (i.e. the stuff that bores the smart kids to tears). Schools that don't pull resources from other areas to concentrate on teaching to the test may see their funding cut, because their students don't do well enough on the tests.

When you talk about the positives of having standard tests, be careful what you wish for, because what shows up may not be what you had in mind.