Thanx for your detailed reply. I checked again in the manual and while it explains a lot without exactly saying much, it seems it's working as expected then, but I can tell you why this annoys me:

When I arrive at a certain fader value with whatever combo of track and VCA level and want to automate that fader, it would only seem logical for me to do that from the exact level state the fader is right now. So, when the fader with whatever combo of its own level and the VCA level is at -3 right now I want to engage automation, do whatever move I want on the basis of that -3 level. So the exact same way as if no VCA track was involved. For me a VCA is foremost a lelvel control for a group of channels and it makes no sense having the VCA offset "double up" only when automating a channel, if you know what I mean.
I wonder if anyone with experience on a classic console with VCA groups can share what's happening there.

FWIW, I still can't believe Cubase's touch automation only works as intended after having manually set a point at the end as users requested fixing this since SX3 at least.