To me it makes mire sense if they are drawing a map at camp then actually on the adventure, in fact it seems like you definitely wouldn’t have the time on an adventure to make a map so I’ve always ruled it that you can only make maps in camp.
Me personally i like the idea that making the map and reading it is a seperate roll. If you have ever walked with a map you do realize how much skill there is to seeing which path is which, you can easily get lost even if you are on some sort of path especially if you are not totally sure of where your actually going.