What about this email is a "shakedown"?
Everything else about the e-mail is clear that it's about the organization, though. I don't know why this person would think they're going to start getting bills "per committer" of the organization where they're not already the responsible party for billing. Like GitHub just decided that they're going to start billing this one person for every committer in the org, but only for this one feature?
Someone appears, gives you a service unprompted(carries your bag of spams some AI code reviews), them later demands payment.
It's not a small print somewhere, or one of these weekly app store subscriptions that run up high bills because someone clicked "Yes" in a game.
It's like calling a Netflix renewal email a "shakedown" just because they send you an email giving you a heads up that your trial will convert into a paid subscription.
And yeah, that how the businesses work: you opt-in to feature, then you start paying for it. Sometimes the latter part is delayed, in which case it's a good style to send heads-up email about it. Nothing unusual or scammy about it.