You seem to take the author's language here as describing early Buddhism, but I think she is describing the observed history of Asian Buddhism, presumably East and Southeast Asian Buddhism. I think this is a clearer reading given that she starts with "Asian Buddhists," focuses on the Burmese tradition, mentions again "for most of its history in Asia," mentions Jack Kornfield who studied in the Thai tradition, etc.
For the language at the end of your comment, this kind of sola scriptura [1] approach is valuable and worthwhile, and it is part of how lay meditation traditions were revived in Asian Buddhism [2] -- but when you describe Asian Buddhist traditions as "later additions ... never encouraged by the Buddha," isn't this what the author has in mind with her next paragraph? Copied for your convenience:
> I want to clarify, by the way, that I’m not necessarily critical of American Buddhist entrepreneurs. The problem is if you mistake this white American Buddhism for all Buddhism, or claim that this is the “right” or “only” way to practice Buddhism.
It's fair is she mentions that she is describing Buddhism as per current SE-Asian practices.
Then it is fair.
> The problem is if you mistake this white American Buddhism for all Buddhism, or claim that this is the “right” or “only” way to practice Buddhism.
But she wants to make the readers believe that her version of Buddhism is the "right" way to do it? And she is rebuking the white Buddhists for deviating from it?
For the language at the end of your comment, this kind of sola scriptura [1] approach is valuable and worthwhile, and it is part of how lay meditation traditions were revived in Asian Buddhism [2] -- but when you describe Asian Buddhist traditions as "later additions ... never encouraged by the Buddha," isn't this what the author has in mind with her next paragraph? Copied for your convenience:
> I want to clarify, by the way, that I’m not necessarily critical of American Buddhist entrepreneurs. The problem is if you mistake this white American Buddhism for all Buddhism, or claim that this is the “right” or “only” way to practice Buddhism.
[1]: https://en.wikipedia.org/wiki/Sola_scriptura [2]: https://vividness.live/protestant-buddhism