Yes, the status is pretty weak if you think of it as some kind of protection from investors. A "public benefit corporation" compared to a regular corporation removes only one specific route investors could use to force a company to do something: a shareholder lawsuit alleging that the company is failing to maximize shareholder value. But in the post-WW2 era, even regular corporations have no legal duty to maximize shareholder value, and can be run according to a number of principles (the belief to the contrary is a mixture of some early 20th century cases combined with a good amount of urban legend about corporate law). Especially considering that nearly anything can be justified as "part of our brand image", and courts aren't interested in second-guessing that: if Ello thinks it's important to its brand image to not show ads, a court is not going to inquire into whether this is a good or bad business decision, regardless of whether it's a public-benefit corporation or a regular one.
All the other ways investors could force a corporation to do something, such as pressuring the board, voting in directors, voting on shareholder resolutions, etc. remain available. If the investors think Ello should show ads, or should sell to Google, or anything else, they have good ways of making that happen (given sufficient share ownership/etc.).
All the other ways investors could force a corporation to do something, such as pressuring the board, voting in directors, voting on shareholder resolutions, etc. remain available. If the investors think Ello should show ads, or should sell to Google, or anything else, they have good ways of making that happen (given sufficient share ownership/etc.).