Because vanilla Generals isn't good enough for you. Realism overhauls and graphical enhancements are the main points of existence of this mod. If you want tons of new units, this is not the mod for you.
Don't mind the lag in the video. This happens when there's a large number of objects on a map which in this case, there is.
Basically, this is a system which allows the player to fire rocket artillery at different angle. In this case, specified as low and high angle.
Why exactly do you need this system? You need it because low angle firing can cause a collision when there's a building in front of your artillery and it sucks for that to happen. That's when high angle firing comes in handy especially in multiplayer games.
Detailed points of the video:
-Low angle firing allows the fired rocket(s) to reach its destination faster while collision is likely to occurs. This mode has further range.
-High angle firing makes the fired rocket(s) to reach its destination slow and less effective in term of impact damage infliction but safer in return. This mode has shorter range.
-Scud Launcher can switch between explosive and toxic warhead, if available, at will with the time as same as its weapon reload time.
-This system allows me to code the Scud warhead changing thingy system to any vehicles. This could mean various warhead for tank shells or even infantries? Who knows what might be done in the future :P
-New optimized effects for variety of explosions which will be shown later on.
-It's unclear that AI is smart enough to use this system or not.