The encircled fuzzy unit in R2 is at level two. The other unit in BB2 is at level zero. Smoke has a height of two levels, i.e. it goes from level zero to level two. Smoke is also inherent so LOS does not have to be visible on both sides of the LOS. Touching the hexside is enough. Since the LOS goes from level two to level zero, the LOS is < level two in all hexes. The LOS goes down the hexside in fuzzy hex S2, through the middle of fuzzy hex T2, then along the hexside of fuzzy hex U2 for a total of three hexes at +2 hindrance, making a total hindrance of +6.
If the Smoke hexes had been (inherent) obstacles, all three hexes would have "plateau-ed" the LOS, meaning the encircled unit could not see past obstacles in those hexes to a lower level. If the encircled unit had been at level three, the Smoke hexes would be treated as obstacles to determine blind hexes. Hexes that would be blind to LOS from level three would be hindered instead. So if the encircled unit were at level three, it would have two smoke hindrances to hex V2.
In general you can think of what would happen if the SMOKE (or most other full-level hindrances) were an obstacle. If it would block LOS as an obstacle, it will hinder LOS as SMOKE. This general principle doesn't work with orchards however, which is a bit annoying.
JR