I agree with this, my only gripe with ssd's is the actual data storage amount usable to the consumer. My Crucial m4 128gb ssd only has 119gb data storage, 9 gb put aside for the actual marvell controller and wharever else is inside the drive before the end user storage.
He's talking about the spare flash that SSD's keep for maintenance and increasing life. The 120GB SSD's do that and have the 8GB hidden (I think), I don't know whether the 128GB ones have 136GB actually and have that 8GB hidden or they just mention it in the specs to make it look better.
It can't be the filesystem, taking up 8GB of space. Could be the conversion to bits to bytes as 128GB -> 122GiB.
It's the difference between the decimal system used by disk manufacturers (GB) and binary system used by Windows (GiB).
128GB = ~119.2GiB
It's not new.
HDD's have been measured that way for as long as I can remember.