I think they're a good thing that disproves the conventional wisdom that corporations are "required" to act only in the profit interests of shareholders, that share price is the only measure of executive performance.
Going further, I believe this canard is promoted by greedy assholes as justification for their bullying of "nicer" people who might have a more holistic view of corporate behavior, something which bullies are psychologically incapable. These people would call PBCs theatrical, "hey bro, good for you!" on par with starting a nonprofit.
I don't know a lot about B-corps so I'm generally talking out of my ass, but it seems like a "hey we tried" get out of jail card if they decide to shed it, which they can always do. If they don't wind up shedding it, do they go for PBC? Overall, maybe it's good for setting expectations, but since there's no legal committment involved I don't see much more to think about it.