The linked articles cites some evidence that moving high achieving/gifted students have a positive effect on their math and ELA achievement. I don't believe that anyone is contesting that having a classroom for gifted students has a positive effect on their learning.
On the other hand, there is a growing concern of the negative externality of this decision on the other students in the larger school community. In other words, we know that having high performing peers have a positive effect on students learning (this is a positive externality of having a desk mate that is gifted). The theory goes that removing these gifted students from regular classrooms has a negative effect on everyone else that remains. Again, this is a process that makes intuitive sense.
The tough sell in this argument is that, at the end of the day, this remains an externality for gifted students. Helping your desk mate does not directly impact you and, in all honesty, might even hurt your chances for a perfect SAT score or of admission at a top university because you took a lower division courses than your peers that were scooped away to a gifted classroom. Parents/families need to make the decision to give up on the positive returns of gifted education in favor of potential learning outcomes for other students or even more remote, long term outcomes of (maybe) less crime or increased tax base 20 years after graduation. I am not sure if this is a viable demand to place on parents/families given how competitive society at large is.