At least it has proper tracks in the trailer and not B1 tracks 😛
However, the video’s description is interesting :
Meet a new IS-3 model with an autoloader in World of Tanks Blitz! Recreated from Soviet drawings, this unique vehicle is the first and only heavy tank with a loading mechanism like this. But only the first 60,000 players who complete the mission will be able to get it. Hurry up!