> So any non-public company would be exempt?

All of the major tech companies are publicly traded.

Being publicly traded is also a major risk factor for hostile corporate behavior, because the top executives of private companies tend to be the owners and care more about the long-term than short-term profits, so it even makes sense as an explicit policy choice to regulate publicly traded companies more than private ones.

Non-public non-cooperative ones actually. Having thousands of members is very common in cooperatives.