It seems some of the statistics and status op-mode commands haven't yet been ported with the xml/python implementation.
1.2:
vyos@crux-test:~$ show conntrack-sync
Possible completions:
external-cache
Show connection syncing external cache entries
internal-cache
Show connection syncing internal cache entries
statistics Show connection syncing statistics
status Show conntrack-sync status1.3-rc6 / 1.4:
vyos@equu-test:~$ show conntrack-sync Possible completions: cache Show connection tracking cache entries