A freeze like this is common and basically just signals that they are ready to get to work with the current team they have. The whole point of the AI org is to be a smaller, more focused, and lean org, and they have been making several strategic hires for months at this point. All this says is that zuck thinks the org is in a good spot to start executing.
From talking with people at and outside of the company, I don't have much reason to believe that this is some kneejerk reaction to some supposed realization that "its all a bubble." I think people are conflating this with whatever Sam Altman said about a bubble.
Historically every technological recolution serves to replace some facet of human labor (usually with the incentive of squeezing profits as technology gets cheaper over time, but wages do not).
Industrial revolution == automate non dexterous manual labor
Information age == automate "computational"/numerical thinking
AI == automate thinking
Robotics + AI == automate dexterous manual labor