There is no reason to expect that the test results would be the same across all demographic groups, and in fact, everything we know about psychometry (i.e. the science of mental testing) suggests that we should expect exactly opposite. See e.g. "Intelligence: Knowns and unknowns", which described the consensus position of the American Psychological Association as of 1995:
> The cause of [test achievement] differential is not known; it is apparently not due to any simple form of bias in the content or administration of the tests
themselves.
Not sure what is your point, the "test achievement" mentioned in the document refers to totally different "test" that the ones we were talking about.
Also, on just pure logic, I don't think the document shows what you think it shows. The document you provide (which is 30 years old, so with just this one, we should not assume it reflects today's consensus) explains that the difference is not understood, and that there is no _obvious_ answer, neither from biology, from group culture or from bias in the tests. In other words: the difference is due to something _not obvious_, for example (but not limited to, of course, it's just an example), _not obvious_ form of bias.
> The cause of [test achievement] differential is not known; it is apparently not due to any simple form of bias in the content or administration of the tests themselves.
https://www.mun.ca/biology/scarr/APA%201985%20Intelligence%2...