A previous dev has suggested that the GTA 6 map really should be smaller and even more densely packed. Even so, as leaks have ongoing to trickle out of Rockstar, modders have recreated the GTA six map in GTA 5's engine which gives a sense of its substantial scale. https://gtasixnews76317.blogprodesign.com/56660611/the-5-second-trick-for-grand-theft-auto-6-trailer-2