Insert blank page was added as a new command in Word 2007. It is the same as inserting a page break, an empty paragraph, and a second page break. You can see this if you display non-printing formatting marks. Frankly, I had never noticed the button.

I generally, instead, use page-break-before paragraph formatting to induce a new page or, where necessary, use a next-page section break instead. Word has gotten better with manual page breaks but I suspect they will still cause formatting anomalies. They certainly add editing headaches, IMO.