Based on conversations with some affected friends, there was layoffs outside of the Meta AI org today too. Not sure if this 600 number is representative of how many people were actually let go by Meta today.
One friend told me she feels every time you reapply internally, as the newest team member you end up first on the chopping block for the next round of cuts anyway as no time to make impact, she will just take the redundancy money this time. Lots of Meta employees now just expect such rounds of job cuts prior to earning calls and she has had enough of the stress.