Because PPRC-XD does not respect the sequence of dependent writes at the secondary, the primary and secondary cannot be assumed to be in a consistent state unless the application I/O is quiesced and data is allowed to drain from the primary to the secondary. Otherwise, the secondary must be assumed to contain a "fuzzy copy".
The only reliable method for ensuring a backup copy at the PPRC-XD recovery site is to take frequent checkpoints during which the application at the primary site is quiesced, allowing data to drain to the secondary, after which a FlashCopy® is made of the secondary volumes.