You mean they are a group of people? or a computer program?
2022-06-08: Lasse Collin said that he had worked off-list a bit with Jia Tan.
I think that "off-list" means not on the xz mailing list, maybe over the personal email/phone/voice app. That's why I thought that Jia Tan was a real person
Do we know who really is Jia Tan? Any photo of him? The email addresses he has been using? His location?