Scheduled emails will not be sent from cross-updated bookings.

Cross-updated bookings are meant to be blocking off date, but not to be used as actual bookings.

You can still send emails from cross-updated bookings, but you would need to make sure that an email has been added to the guest details.
Furthermore, if the original booking is being updated, the additional guest data will be wiped when the cross-updated booking is being updated.

You can still send manual emails from within the cross-updated booking.
For information on how to do this, please see this help centre article.