Actually I’m not sure what having Nat assigned to the Fishing Shack does. I removed him from the Shack at the Architect Table . Then I deactivated him at the Command Table in order to replace him with another follower I got from the Inn . He’s still at the Shack selling stuff and offering quests for Lunkers.
Nat still visits me when I am fishing
I am not fishing in my Garrison because I have read I can’t catch Lunkers there. Turning in Lunkers for rep and to buy stuff seems to be the only reason Nat is there. I don’t need him as an active follower to do that.