True for doing orientation. Not so true when running a game. The players are doing a dungeon crawl. You are describing the room. The standard way of doing that is through compass points- there's a door in the west wall, there's a mural on the north wall, etc. Now, with a map that is rotated 90 degrees, you have to remember, every single time you look at that map, unlike the 10000 other maps that you've seen, this one is different. You have to remember that this one, unlike all the other ones, puts north to the left, so, now, all your room descriptions have to take that into account.
It makes using the map a lot more difficult, mostly because the other 99% of the maps you will use in D&D will orient north at the top.
Are we talking about different things here? Because, I'm talking about using maps in D&D during play. That's all I'm talking about.