Does the monitoring agent poll for metrics, or does it look at differences in performance counters over time?

I noticed recently that a batch job I’m running every 3h has far lower reported Disk I/O than is actually occurring (0.3 B/s rather than 30KB/s over a 20 minute window).

Most of the disk activity is concentrated in a small subset of that 20 minute window, so plausibly the monitoring agent is polling and recording the small amount of changes to file metadata and whatnot while completely missing the bulk of the data being written (as opposed to recording total changes since the last time the monitoring agent examined the disk).

Does that explanation make sense? Does the monitoring agent poll for current throughput, or is there something else going on?