I sometimes need to mass delete large numbers of small image files or empty the recycle bin in my Android phone (Google Pixel 8).

A typical case would be deleting 100 thumbnails produced by some app, each 10 KB in size for a total of 1MB.

When I do this via adb and terminal commands, it takes very little time, most often less than a second. But if I use the photos app on the phone to empty the recycle bin or select many images and then delete, it can take 20-30 seconds or even more.

Why is it so slow? What does it do in addition to deleting the files, that takes so long, even for very small files?