Maybe? A4 looks substantially narrower than A3 in terms of page ratio. You'll want to make sure you've made sufficient space for the bleeds as the lines for each will be different. It'll likely affect your gutters more than your outer bleed edges. If you're going from A3 down to A4, then manage the width and put white at the top into the bleed areas if needed.
I actually have a few US released manga that have done that sort of treatment of adding white borders. Japanese manga are printed in tankobans and then smaller books, and both generally agree with each other on scaling sizes, but US manga uses a more "American" standard size for their books, and as such, a lot of the mangas have scale issues
(YuGiOh and a lot of those standard print manga are odd scaling, larger than JP's small books, but off in ratio. Higher quality print releases, usually from the popular boy's love manga's by June iirc, are printed still larger than JP's small books, but on better quality paper and the ratio is correct mostly)