eContent Pro International Press is confused.
https://www.researchinformation.info/news/u-s-book-publisher-launches-under-platinum-open-access-model/
It says it's “the first U.S.-based book publisher to operate exclusively under a #platinum #OpenAccess publishing model."
But it also says that "the open access processing charges that offset the publication costs are funded by individuals, sponsoring institutions, grants, and so on" and that it's "committed to offering some of the lowest Book Processing Charges (#BPCs) in the industry."