LOS on slopes

[Blackcloud6]

There is nothing wrong with the rule as written.  It was a deliberate design choice likely to assume where the crest line is on that hilltop, nor having to figure out what the angle of slope actually is.  The designer decided to say that the majority of the soldiers in that hex are not in a position to fire on the enemy because they are on the down slope of the other side of the hill.  It is simple to understand and adjudicate.  

Changing the rule to be what you want it to drastically changes the nature of the game in this case.   

Furthermore, the rule actually allows one to use reverse slope tactics which is a very realistic and important tactic in tactical games of this scale.

Almost all design choices are tradeoffs in complexity vs. simplicity vs. realism interpretation and "design for effect."  It could very well be that the designer of the rule decided that ability to conduct reverse slope defenses was more desirable than allowing units to see from behind a notional and undefined crest line.