Does properly exploring a hex help with Navigation?

I’m currently running Tomb for the first time and have a bit of an odd ask. I’m mainly asking this because one of my players is running a character who’s really into maps and wanting to map the island. If the party succeeds on a proper navigation check for the day and I clear one of the hexes on the map, then say they want to go back exactly the way they came. Do I still need them or their guide to roll a navigation check? Or is that only for when they move into new hexes?

And if the players characters have the map from Syndra Silvane and are trying to fill it in too, does that help them with checks at all?