Just FYI, I have contacted Grant Thornton directly and am awaiting confirmation that this email and the "Claims Portal" are indeed legit or if it is another 3rd party "scam" like that cryptopia rescue outfit... I'll update if/when I get a response.
I also contacted them, several hours ago. No response.
They said in the last update: "...note that any communications relating to the Liquidation will come from the official channels such as the Grant Thornton website, or the Grant Thornton and Cryptopia Facebook and Twitter accounts." I don't see an update at those official channels.
This appears legitimate, it goes to the valid domain... but, very unprofessional all around.