Just a guess but I would say that most users were using less than 100 volts so the new drives use 100V rated parts, as they are cheaper and have better electrical characteristics. They have a safety factor built in to make them more durable so they are rated down around 80V. If you want to use the higher voltage, do what I am doing and wait until Tero releases the new high voltage version, which will be rated at 160V.
By the way Tero, how is this coming along? Seems there hasn't been much progress on this. Is it due to lack of demand? I have 14 Motors which are rated at or above 100V and I'm waiting to buy a couple. Can't buy 14 though, I'm poor!