If you look on GIT there is an unsupported version that has been tweaked to work with 700 but it would be hard to include this in the release version for a few reasons none of which are because it is technically difficult to add support.
When 700 was first released the only supported way to integrate with it was via a Z/IP library written in C rather than the serial connection that the current binding uses.
Early versions of this library had significant shortcomings.
The new library does not support anyone’s current USB stick so everyone would need to rebuild their networks.
Rewriting to use the library is a substantial piece of work and supporting both old 500 and new 700 would be very hard.
It is still not clear if this will remain the only way to interface and be approved on 700 and beyond but possibly it will change now the standards have changed to be managed by https://z-wavealliance.org/ .
For the US z-wave has recently moved forward with a higher power setting and the promise of longer range and higher node counts.