Where does the game get the Unstable Rate value in osu!catch?

Where does the game get the Unstable Rate value in osu!catch? - Gold bitcoin coin on background of growth chart

If you completed a beatmap, you will be presented with the results screen, and hovering on the Performance Graph will show you this:

The information shown upon hovering over the Performace Graph

This got me thinking, osu!catch is not really a timing based game, so why does it show the unstable rate and hit error? Where does it get these values?

According to the osu!wiki:

Unstable rate represents the consistency of the timing of the hits, where lower numbers are better (top players often score below 100). Note that the value measures consistency, not accuracy, [ ... ] The formula is essentially the standard deviation of the hit errors (in milliseconds) multiplied by 10.

Here's the problem: osu!catch is not a game mode where you get high accuracy by timing the notes but you get high accuracy by catching more notes (or fruits). The osu!catch's accuracy formula shows this.

osu





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『osu!』BeastrollMC explains Unstable Rate




Sources: Stack Exchange - This article follows the attribution requirements of Stack Exchange and is licensed under CC BY-SA 3.0.

Images: Ivan Babydov, Tatiana Syrikova, Matthias Groeneveld, Karolina Grabowska