In a game where weapon ranges and terrain are abstracted, I don't really see why 'true' line of sight is used. What if the model is crouching? Does that mean he is physically unable to stand? Does that mean his standing mates get shot behind a low wall whilst he's safe? It doesn't seem logical to me.
Having said that, I'm sure any sort of system will have its glaring faults, so I guess if it works, then it works.