some parameters can be exploited to expose the modulation depth settings in a useful exploratory way
there are synths/parameters/machines where the strike velocity will instantiate a non varying audible event,
the purpose of this velocity slider is analogous to both a meter and to a partial fake controller (the controller side works out MUCH better for aftertouch as this is attached to many more parameters which are variable after initiation)
The aftertouch (or modwheel typically on most other devices) is the ‘template’ for this velo-mod screen you are immersed in - this is why i discard the text you highlight as superfluous - there is no concept of range (it’s more of a documentation clarity issue imho)
The virtual slider (for either velocity or aftertouch) is both a ‘meter’ and also an ad-hoc ‘controller’
in both cases - when live playing the meter will react to your input (a single velocity snapshot or a continuous monitoring of pressure) and in both cases (for certain parameters wrt velocity) you can use this slider controller like a ‘virtual’ input
That’s why i described the case of using oscillator detune (on a droning note) as it’s the only meaningful way to make this utility work for you - it’s simply working with more constraints than e.g. the virtual aftertouch slider does and it’s clearly more difficult to use this virtual velocity slider on transient sounds (thus recommending pre-programming velocity steps into a sequence) - you can modify the effect of some velocity modulations using this virtual slider