> The government controlling social media platforms is vastly different from a collection of companies controlling social media platforms that they built

If the difference is measured by the effect produced then in many cases it is zero, that is, there is no any difference. For example,we frequently see collective censorship which effectively means the absence of freedom of speech.

In fact, there exist also other interesting forms like collective (or democratic) racism or collective (democratic) totalitarism. For normal people, the origin of these rules does not really matter.