At first, I assumed that writing meant the act of writing something down. However, the tag wiki says
Focused on the aspects peculiar to Japanese in its written form rather than the spoken form.
If the tag is supposed to cover reading (not to be confused with reading!) as well as writing, would written be less confusing?
For the record, the oldest question that currently uses writing is How to write hiragana and katakana in Windows? . I assume it was the creator of the tag, but I can't be certain.