The count of groups in distributed grouping environment only show results from shards used in the second pass.
How to reproduce :
Ask for only 1 document (ROWS=1) in a 2 shards environnement with GROUPS.NGOURP=true and of course with GROUPS.FIELD=fieldA.
It will only display the total of a shard (the one used for the second pass)
Expected results :
Sum all groups count from ALL shards.