If you are on a hill ( maybe 2 hexes away from the edge i.e. M11 is firing at K10) and a unit is on the ground- do you see it? It says something like if a hill hex is between you and the unit- you can not see it- but does that mean 2 different/seperate hills?
Someone said to think of hill hexes as plateaus, with the elevation change being the hexside with the gradient lines. If you think of it that way, M11 not having LOS to K10 makes (at least some) sense.
Edit: My original explanation didn't apply to your example.