They constantly say they are a Public benefit corporation but there is no actual difference between that an a corporation. This leads to people assuming some kind of benevolence.
Wrong. B Corp boards are legally protected from lawsuits if they reject the highest bid when they put the company up for sale. In a C Corp, once the board puts the company on the auction block, not taking the highest bid, even from a company that's diametrically opposed to the goals of the C Corp, opens the board up to lawsuits from shareholders pissed about not getting the maximal return. Suggesting this is no difference shows a lack of understanding of the legal regime these types of corporations operate under.
B Corps allow the board to weigh things besides shareholder value. That's a meaningful distinction.
The idea is that shareholder primacy isn't compatible with everything every corporation wants to do, so having a board that's protected from lawsuits when they put things above shareholders is a useful thing and B Corps offer that.
The board can, for example, reject a "superior" takeover bid without fear of lawsuits from shareholders pissed off they didn't get the biggest payday available. A typical C Corp's board MUST take the highest offer, and not doing so WILL get them sued. That means if GoodGuy B Corp is about to be taken over by BadGuy Inc., the GoodGuy board can say "No, they're not compatible with the public benefit mission we incorporated under so we're not going to accept their offer." That's actually really useful.
No GoodGuy B Corp would still need to fear lawsuits in that situation and PBC or not they would be able rejecting that decision. If they get sued there is a good chance they can defend the decision.
I'm not going to speak for OP, but I definitely remember it also being a rallying cry for Bluesky too. "No one person can control the network blah blah blah"
That's not at all incompatible with Bluesky having a funded company with a CEO.
The term they use for this is "credible exit" - designing the entire protocol such that if the company itself misbehaves the affected users can leave to a separate instance without losing their relationships or data.
Bluesky's claims of being decentralised were always way way ahead of the de-facto reality of it. That's not the same as Mastodon.
It has been a "rallying cry" but it doesn't stand up to much scrutiny of how Bluesky actually functions: an "open protocol" with one central server means little. Maybe this will change at some point in the future, and maybe it is changing, see https://blacksky.community/ . But this is not the same as Mastodon, where it's been that way for a while.
