Given what I found out in this thread, that the manual contains a lot of things that haven’t even been implemented yet, I guess that this could be a similar thing.
Thinking about it, I don’t know what a sensible default that can’t be changed would be for Note Off Velocity. I mean, I guess it could be cool to for example modulate the release time (so that a high Note Off Velocity would result in a fast release and vice versa), but this isn’t a behavior that I would like to have on every single patch.