It didn't explain the goals well enough to parents, and many teachers didn't have the number sense themselves leading to many of the examples are passed around showing how the whole process is broken. There is also a question of if even works well, as it is somewhat akin to teaching someone the shortcut on how to do something before they have mastered the long way of doing it. Many experts in their fields have shortcuts, but they don't teach them directly to juniors in the field as there is value in learning how to do it the long hard way, as often times shortcuts are limited and only an understanding of the full process provides the knowledge of when best to apply different shortcuts.
> There is also a question of if even works well ...
No, it doesn't. And that's one of the main tragedies in modern discussion about education. A lot of people think that we have to teach the way how experts think. But it doesn't work.
Take a look at programming for example. Everything you ever really need to know about programming, can be described in single A4 probably. But it has no any use if you learn. It even makes things worse, because it's a thing you have to pay attention to, but you don't really understand. You have to learn via small babysteps, automate a lot of small things in your brain, practice a lot etc. There is no shortcuts in learning.
It didn't explain the goals well enough to parents, and many teachers didn't have the number sense themselves leading to many of the examples are passed around showing how the whole process is broken. There is also a question of if even works well, as it is somewhat akin to teaching someone the shortcut on how to do something before they have mastered the long way of doing it. Many experts in their fields have shortcuts, but they don't teach them directly to juniors in the field as there is value in learning how to do it the long hard way, as often times shortcuts are limited and only an understanding of the full process provides the knowledge of when best to apply different shortcuts.