Then explain why my daughter's 2nd mathbook teaches subtraction SIX different ways. Yep, lots of A/B testing there, lets just try every possible, confusing metaphor so the kid doesn't master anything.
Or did you think everyone learns best the same way?
Wouldn't that make sense? I feel like bad textbooks have given the idea of text books a bad name. And I don't think this is a "no true Scotsman" fallacy. It's more an issue of mostly horrible Scotsman written to align with ridiculous state standards.