Wow why would they give GrapheneOS such a marketing boost?
I don't think they're lying, after all if they did they'd lie about much more common mobile OSes too. But personally I wouldn't inform the public of my weaknesses if I were a 'security/forensics' company.
Because they want to advertise that they CAN break into phones loaded with GrapheneOS. Just not the latest version. Likewise they "announce" that they can't unlock BFU iPhone-s running latest iOS, and the real message is "we can unlock just slightly older iPhone-s and you may expect us to be able to unlock current version after few months".