Yeah I saw this too, but I suspect that it was originally intended to be part of Memories of Reach and was later scrapped for some reason. He also has a video showcasing a H5 anti-air wraith which was pretty sick.
This was practically finished too... Even if it was scrapped from MOR, this should defiantly be shoved into a future update due to popular demand.
There was a req variant where the projectile burst into a "firework stream" as well like the charged up plasma caster. I assume we'll get it now since it was uncovered.
I agree with Given, Multiplayer team probably scrapped it, but now that it's uncovered, might as well give it to us or succumb to more lazy 343 remarks.