That's a fair point about what you expected to read. That said, while I agree that "teach to the slowest learners" is common and results in flatlined learning for at/above-grade-level students, I would argue it's somewhat orthogonal to the claim "disagree with the premise of maximizing learning."

If you teach to the slowest learners, then it's still possible you might agree with the premise of maximizing learning (for the slowest learners). So, I can't use "teach to the slowest learners" to argue that many people disagree with that premise in an absolute sense (for all learners).