To me it's all pretty clear... which may mean I am completely wrong.... but..

a.) In heavy forest/jungle you can't see the target but you still have to suppress them, so high volumes of fire across broad arcs is merited. The physics of dispersion means this will only work at pretty close range.

b.) At longer ranges, your fire has to be directed either at the enemy that can be seen, or at his suspected position, so more deliberate aimed semi-automatic fire would seem useful. This would also apply in the urban terrain.

Translating that into training may require some thought.