I thought this was the common way (gibi that is) to refer to harddrives in the OS, I thought that that was the reason harddrives were 100gb when i bought them but only showed up as 93gb on my computer.
It used to be common to speak of sizes in "hard drive megabytes". Eventually, the disk manufacturers won the pointless semantic battle and that went away.
In practice, it matters not in the slightest.