[kisito]

I had no luck visiting the link you offered. I guess it is a China problem where lots of sites get blocked.
It seems to me that you have a slightly different situation in Japan. In China, they have to cope with the complex and difficult nature of English grammar. Chinese grammar is fairly simple and lots of complex English grammar forms like tenses is new to the Chinese student. If you study Chinese, you will enjoy the ease of learning verbs without bothering yourself with changes in tenses. So I guess that is why some schools do not get it right with the introduction of English grammar at different levels.Japanese grammar I was told is more complex than Chinese grammar. The Heads of English Departments in China seem to be aware of the difficult and complex nature of the grammar, but the W5H questions of introduction are not properly considered.To make matters worse , too often I come across education departments with people who have little or no training, deciding course materials for towns and cities.
Students are either flooded with too many complex forms that confuses the heck out of them at an early level, or simply left unaware of these complexities that when they eventually come across them, they see English as a painful language to study.
When I asked one Chinese English HOD why she recommended a course book for her school with so many complex high level grammar forms for her primary school kids who were just about beginner and elementary levels, she told me simply "So that their English will improve rapidly."
I am not a grammar expert myself, but I can see the logic of teaching various grammar forms at the right time and giving students constant practise to consolidate what was learnt. I might just be babbling myself, but I am just trying to contribute.