I don't know where you get your information, but Berzerk was licensed by Atari from Stern. They made a game for the 2600:
https://www.atariage.com/software_page.php?SoftwareLabelID=29
Most recently, Atari purchased the rights for Berzerk from Stern:
https://atari.com/blogs/newsroom/atari-announces-acquisition-of-berzerk-and-frenzy-ip
The fact that Atari had the game on their system and because they purchased the IP to it technically makes it an Atari game now. What they choose to do with it is all up to them.