BackupCursorHooks send a copy of the storageEngine pointer on startup, construct BackupCursorService with it, which will be invalidated after FCBIS.
1 - BackupCursorHooks::initialize(serviceContext, storageEngine);
2- initializer registration
3- BackupCursorService construction

hence BackupCursorService fails while trying to use it to open backupCursor:
_storageEngine->getLastStableRecoveryTimestamp();