Its always seemed kind of redundant from my understanding of them too. Though I think its just a terminology and technicality thing here. The CC drivers self-adjust their voltage as needed based on their load. As soon as you make a manual adjustment of the voltage its no longer variable voltage and considered constant at that voltage you set.
True constant voltage drivers are usually 12v or 24v and usually drive diodes designed to only operate at that voltage with minor variances.
To me, it seems like it would only be useful to have both when dealing with things that werent specifically designed to be run by the drivers we commonly all use. Shit with really weird voltage requirements that arent covered by the ranges we typically use, a fixture that cant handle pwm dimming, or for someone wanting to fine tune for efficiency.
I believe its the A and AB versions that have the ability to internally adjust the voltage output so all of those versions are considered cc drivers + cv capability.
Interestingly an exception to this is the HLG-320H-54AB. It is identified as a constant current/constant voltage driver, however according to the datasheet, only current is adjustable on this driver.
And the plot thickens.
That one is one of the only true CC/CV ive seen from meanwell its locked at 54v and 5.95 internally and has a PWM dimmer on the output like the other B and AB versions.
The PWM dimmer pulses the output to modulate current down to less, but the driver itself is still outputting 54v/5.95a to start with.
I think the simple answer here is that not all LEDs are dimmable so sometimes you do need to be exact with both voltage and current.
I spent a lot of time trying to get a good grasp on these things last year and this is my understanding, but as always I smoke everyday from when I get up until when I go to bed so I could be totally talking out of my ass here.