The website haveibeenpwned says the original breach date was 18 December 2020, with the information becoming available on 18 July 2023, with a total of 3,943 compromised accounts. The site notes that as well as all the above information, the leak even includes each individual’s t-shirt size.
Looks like someone in charge of organizing that event got phished. This seems like the type of info that can fit into an excel sheet.
I’ve been reading articles for years about how Google say they’re going to open the RCS API to 3rd-Party apps but they have yet to do so.