It is, I can't link on my phone but a YouTuber did testing on both maps and presents a lot of evidence as to why they're the same size. He compared both in game maps using the same unit of measurement (he shows how he was able to do that) and then transverses both maps on foot (sprint enabled) with nearly identical times, but it's important to note that sprinting in fallout (outside of power armor) is a bit faster.