PostgreSQL Instances Overview dashboard behaves differently compared to MongoDB or MySQL Instances Overview.
On pmmdemo.percona.com, selecting for example Node Name "pg11" the dashboard still shows information for all nodes. "Node Name" drop-down only filters items in "Service Name" drop-down but not in the dashboard. See attached screenshot 1.
Both MySQL and MongoDB Instances Overview behave more logically: selecting Node Name actually filters the dashboard as expected, as screenshot 2 shows.