Right, I see that now.They aren't directly managed by ICC, but it is the website given directly by them.
But you definitely don't need to send your passport. That's straight from the federal government there.
Applicants from visa-exempt countries
The ‘Passport Request’ letter instructs the applicant on how to send a photocopy of the bio data page of their passport and, if applicable, the bio data page of the passports of their accompanying spouse and dependent children.