Question about map-making

So I am in the beginning stages of building a fantasy world, and I’ve been working on a map. I can’t remember where I heard this, but I’m sure I read somewhere that if you’re making maps of fictional places, you should start by making maps of real places to get a grasp for scale and relationship between regions. Has anyone heard this before? If so, where did you hear it, and do you have any thoughts on the idea? Should I bother learning to draw maps of real countries and then move on to the fictional ones, or should I just jump into the fictional maps? <br>Thanks