I have repeatedly questioned my Japanese students about history teaching. Official textbooks play virtually no role in what (little) they know about Japanese history.
In response to an open ended question, they cite first historical manga and second television costume drama.
The uniform response has been that history is NOT a major subject. If it is taught, the emphasis is premodern.

The only thing textbook approval guarantees is that when a particular textbook is adopted in a particular jurisdiction, the kids get a copy.
Whether a teacher uses the textbook and if it is used is a completely separate question that can only be answered by surveys. Just because the national curicculum calls for history does not mean it is actually taught. Judging by newspaper articles, it is not uncommon for schools to use some or all of the time nominally dedicated to history to teach subjects of more significance on entrance exams. And, in schools lacking a large proportion of students aiming high in the university pecking order, much less is taught and still less is learned.

However great their symbolic significance may be, history textbooks are NOT a major factor in what Japanese do or do not know about their own
history. The widespread assumption that what is or is
not in school
history textbooks determines what children learn about Japanese history is wildly naive.

EHK