I think what he means is that schooners specifically were made to be able to port/anchor in shallower waters than carracks and other long-haul oceangoing ships. Schooners were sometimes used in lakes and rivers as well.
But that's just what I think, based on extremely limited understanding of the material. Hopefully someone can clarify and/or correct me.
Smugglers would prefer shallow draft ships, because they couldn't dock in a regular deepwater port. A shallow draft would enable them to load/unload anywhere along the coast.
But that's just what I think, based on extremely limited understanding of the material. Hopefully someone can clarify and/or correct me.