In Ultimate Doom E4M1 one of the first sargeants wakes up right away when the level starts and it is teleported to shoot the player. The player doesn't need to move at all.
The sargeant is behind a wall and should not be able to see the player at that point.
The sarge is in there in med and UV skills. It's easy to check what happens from the automap by running Vavoom and hitting the console commands:
am_colour_thing "ff ff ff"
Wed, 28 Jul 2010 23:48:11
There has been a big number of chanes of things related to the sight checks, maybe there's something affecting this... there's a chance that it can't be fixed, but we'll see.