At some point since I started seeing this buzzword "authenticity" bouncing around the net, I began to think along similar lines as you. There is definitely some bullshit mixed in with any professed authenticity. And it seems especially true in the context of internet influencers marketing themselves, or teaching others how to market themselves. "Be your authentic self" they say, because that's what captures peoples' attention and will ultimately make you money.
The problem is, it can be hard to determine the authenticity of someone you've never met in real life from something they've written. When people who are trying to market themselves understand that authenticity works to influence people, you've got a recipe for a new brand of bullshit. Fake authenticity.

And that's fine. It helps us to fine tune our bullshit detectors. And ultimately it doesn't matter if someone is really being authentic or just faking it, as long as I find some value in the wave function of their words. No need to collapse it to binary.