...Primocache will calculate the given drive's actual write block size, the deferred write cache will gather together the to-be-written blocks and write them to the drive (when adjacent to one another) as write block units. In the case of my SSD, this would be an erase block of 1 Megabyte (or perhaps the smaller 8K sub blocks)
If this is not my imagination
then showing this on the statistics page or even one of the columns next to the drive letter itself in the upper GUI area.