OK, a possible BUG

In Grid view (mine is showing 7books x 3rows)
Using the Page down key, The focus moves 1 row down
Using the down arrow key, The focus moves down 1 row
Shouldn't the PgDn move down 1 full screen full (3 rows in my case)?
And because I am contrary

Why have both the Cover Browser AND Grid View?
I do realize that the cover browser is detachable AND you can still see the list view (either way), but other than that, they both seem to function the same.