It is a promise from Bluesky specifically, not the entire atproto "atmosphere", as they call it. This is ultimately no different than if Twitter promised such a thing, but couldn't stop people from still scraping the site.
https://www.theguardian.com/technology/article/2024/may/07/j...
My opinion: he's probably trying to avoid legal trouble that would come from propping up a Twitter competitor after making a major sale. Especially one that was initially conceived within Twitter itself