^^I agree with you—I think it's common knowledge to those of us who have been around Japanese music for a while and know what the music scene before was like. But there are also a lot of people (esp. after the literal storming of
Arashi, this phenom of
AKB48, and the relatively recent worldwide exposure of our namesake
Hamasaki Ayumi) who may have not been (for lack of a better word "properly") exposed to the music scene before us, and would probably not know how crazy the music market was back in what many others would call the "Golden Era" of sales in the '90s and early '00s (which is made clearly by the chart on the bottom of the initial post—the whole top five is all from the '90s), and may have also not known about Amuro Namie's single.
I just think because they do have the final numbers in the chart (which I assume is for comparative purposes), they could have mentioned Amuro's as well.
I also totally understand this article was mainly about
first week sales, and I just wanted to mention Amuro's final sales since there is a chart which also mention the final sales for the other highest debut week sellers. I thought it was important (and interesting) since this article mentioned her as the "runner-up" as a female artist to their first week sales, but I guess it wasn't to everyone else.