this is not a glitch, its basically a modded class.
You see when IW made the game he had also made two extra deathstreaks which were hidden in the game and not selectable.
The deathstreaks were:
Care Package - You get a Care Package on death (Once per game)
UAV - You get a UAV on death (Once per game)
In doing so these deathstreaks, or any deathstreaks even equipment and perks can be hacked into the proficiency slot of the primary or secondary.
I've done this on the PC version. When you hack it as a proficiency you have it everytime just like a normal proficiency. To get it back you simply switch weapons. Pause the video at 19 seconds and you'll see he as the checkered box for his primary proficiency.
Its not a glitch hes just trying to get subs.
The following 5 users say thank you to TheJaRniBoi for this useful post:
yeh IW probs removed that deathstreak cause they woud knew that alot of players would abuse this. Simply die a few times till you get the package, use tactical insertion and then blow yourself every time u with C4 to get new packages.