I think part of the problem here is the values displayed in that column, as it is showing 4,3 MB/s (MegaBytes per second) in your image, which isn't a value I would associate with Hard Drive activity/usage and how this is converted to arrive at 100% of what. I'm not even sure this figure is accurate, as 100% of what your disk being full or 100% activity.
All I can think of is Avasts Service is accessing 4.3Mbs of data per second, but then every value in that column when added up would have represent the physical limit of data accessed per second. Even in your previous image the Avast Service was only showing 1,6 MB/s and at the same time Disk was showing 100%