There is quite a bit of difference between "it is the norm to be fired on the spot and without recourse for something that has nothing to do with your job" (a direct quote, I don't believe missing any context but open to counterarguments) and "a legal framework exists in which a thing could conceivably happen, even though it doesn't happen in any statistically significant numbers"

Even if it does not happen in significant numbers, such possibility and few widely-reported cases cause chilling effect.

Fair enough; the comment is a bit hyperbolic. The larger point that this lack of protection in some sense reduces freedom still stands.