How can motion sensor react instantly (ZHA) if IoT class Local Polling

I have (yet another) question concerning fundamental concepts in HA.
Like the title suggests, I found out that ZHA is classified as “local polling”. So far so good, but as I researched here on the forum, the default scan interval for this iot class is set to 30 seconds. What am I missing?
Obviously my motion sensors for instance report a movement as soon as they detect it and automations will turn the lights turn on as they should. Even the HA frontend “Dashboards” (not lovelace :slight_smile: ) will show me the coloured indication that a movement has been detected.
So where exactly do the 30 seconds come into play? I would expect to see a delay somewhere…