1,200 of 33,000 employees amounts to 3.6% of the work force. This level of action, 1 in 25 employees, gives managers an opportunity to release employees that looked good in the interview but did not meet expectations. Whether Tesla conducted this in a proper manner is open to debate and perhaps details will emerge if/when any former employees pursue Tesla in court. But any company needs to address the inevitable hiri…
If the lack of promised performance reviews is accurate, that's the obvious issue - it implies a labor force decision disguised as a performance decision. This is a pretty common move in e.g. game development, so it certainly isn't unthinkable.
The point about total workforce size is well taken, though; this still seems like it could be as simple as "times are tough so we're cutting more stringently than we might otherwise".