Not the physics, you're absolutely right about that. But if someone is starting from Flintstones foot brakes just getting them to use the real ones is a step up, and the consequences of locking up a rear brake are much lower.
In a controlled environment with a competent teacher and a willing student, you're absolutely right to focus on the front brake. It's better long term, because I've seen guys who have been riding for 20+ years who won't touch the front brake for anything - these are the same guys who don't believe in counter-steering - and it's better not to learn bad habits that you then have to unlearn.
In a controlled environment with a competent teacher and a willing student, you're absolutely right to focus on the front brake. It's better long term, because I've seen guys who have been riding for 20+ years who won't touch the front brake for anything - these are the same guys who don't believe in counter-steering - and it's better not to learn bad habits that you then have to unlearn.