and for completeness, the actual command I was originally having issues with, works as well now:
pd-san2::*> statistics show-periodic -counter total-recv|total-sent|data-recv|data-sent|cluster-recv|cluster-sent|cluster-busy
pd-san2: cluster.cluster: 10/22/2021 17:27:55
total total data data cluster cluster cluster
recv sent recv sent busy recv sent
-------- -------- -------- -------- ------- -------- --------
75.9KB 24.0KB 50.1KB 1.37KB 0% 22.6KB 22.6KB
282KB 28.6KB 258KB 7.21KB 0% 21.4KB 21.4KB
479KB 146KB 339KB 8.82KB 0% 137KB 137KB
pd-san2: cluster.cluster: 10/22/2021 17:28:02
total total data data cluster cluster cluster
recv sent recv sent busy recv sent
-------- -------- -------- -------- ------- -------- --------
Minimums:
75.9KB 24.0KB 50.1KB 1.37KB 0% 21.4KB 21.4KB
Averages for 3 samples:
279KB 66.3KB 216KB 5.80KB 0% 60.5KB 60.5KB
Maximums:
479KB 146KB 339KB 8.82KB 0% 137KB 137KB
I dunno. at least it works now though!