That is not true. During the Digital Security by Design programme UKRI was shipping Morello boards to organisations that requested them. Since DSbD is over, the CHERI Alliance has taken over that initiative. You can request an Arm Morello board via the following link:
https://cheri-alliance.org/discover-cheri/cheri-products/mor...
Also, you can buy a Sonata board with CHERIoT from Mouser:
https://www.mouser.co.uk/en/ProductDetail/NewAE/NAE-SONATA-O...