That is correct, but this means you waste several game days through constant traveling. I have no problems with that, generally, but I also like to be efficient...
However, it is indeed great of one can get most of the maps in the early stages of the game, because then he will have his pick of extras - items, units, etc. In this case, if one is willing to waste like 6-7 days, sneaking, stealing and utilizing the XP shrines (the XP gained is based on the area the shrine is in, not by the char level, so it's great) and finish the game on day 20 or so, it's perfect
I'm also considering such playthrough, just for the fun of it. Starting the game on lvl 8-10 with a bunch of T-Rexes and good backup units? No problem