If the dropout faces rearward enough it'll still be effective. What needs to happen is the dropout needs to not allow the brake pad to be the pivot point for re

If the dropout faces rearward enough it'll still be effective. What needs to happen is the dropout needs to not allow the brake pad to be the pivot point for removal. But a rearward wheel removal path is problematic for other reasons: hitting the downtube during removal, requiring caliper removal to allow the rotor to clear, etc.