Select port polling on Juniper MX routers doubles polling time

When going to settings > misc and selecting ‘Enable selected port polling’ actually almost triples the polling time from around 250 secs to 720 secs. The funny thing is what I run this manually using the collect-port-polling.php script to see what savings I can get in time, it actually shows a about a 20 second decrease to around 230 secs.

Is there anything that would cause the polling time to increase by enabling this feature?