DPI controls counts per inch
DPI describes how many sensor counts are associated with one inch of physical movement. It is mainly a spatial sensitivity setting.
Polling rate controls report frequency
Polling rate, measured in Hz, describes how frequently the mouse reports input. Common values include 125 Hz, 500 Hz, 1000 Hz and higher. It is a temporal property rather than a measure of physical sensitivity.
Changing one does not automatically change the other
A mouse can have a high DPI and a low polling rate, or a low DPI and a high polling rate. The two settings solve different problems and should be evaluated separately.
Why browser tests have limits
A web page can observe pointer events, but browsers may coalesce events and do not expose every hardware detail. The site's polling-rate test therefore provides an observed lower-bound style indication rather than a certified hardware measurement.
Use the right metric
Use DPI when comparing physical movement sensitivity, polling rate when discussing reporting frequency, eDPI for same-game sensitivity comparisons, and cm/360 for physical turn distance.