nealry all (human) characters in games are scaled to 90-99% of the playerheight. its because you as a developer have to guide the players view. details in most games are on ground/playerheight, so you have to force the player look down. that is how you can use lowdetailed parts on the higher leveled modells to save polycount (in addition to the fact that higher leveled objects are more away from you than things on a desk). its also an optical trick to force a deeper room, and also most of the players have the habit to aim UNDER the middle of the screen because of gun-movement through recoil. when you scale down the enemy, headshoots are easier possible.
and in addition its a mental trick. cheap/normal enemies are smaller because you as player are stronger in most games (when carrying a weapon). when a boss/big char appears, your brain says "DANGER!"
these are force-tricks out of the painting/photo/movie-business.
look for the effect of "bottom view" and "top view".
fpsc has forced this a little too much, some of the chars are on 80%^^
just for info @teabone.
1st screenie: weak / 2nd screenie: power!