Villagers can drop food from any sources other than fishing to dock when their job changed to fisherman

[Arina Tei]

Update 36906 introduces a new exploit involves with the new fisherman buff.
If you task the villagers to gather food from any sources other than fish, and then switch their job to fisherman, they can now drop the food they're carrying to the Dock despite the food isn't being obtained from fishing.

[-Dare Devil/x/]

-Pretty sure this is the same way it works for farms as well.