The information I am passing on to you, is straight from the factory not from VWCVUK. They are aware though, but I don't know if they have communicated it to any or all VWCVUK dealerships; I do know that the Breeze group are fully aware.
I am also aware that some of those VWCVUK dealerships have fitted lowering springs to ACC and or DCC equipped vehicles.
Both ACC and DCC are factory fitted and calibrated to a set ride height with tolerances that allow for the usual driving conditions you or I would expect to experience.
By lowering or raising your T6, both ACC and DCC are taken outside those tolerances and VW will not guarantee the functionality of either ACC or DCC; and in both cases it raises a safety concern.
ACC as you are probably aware can be adjusted for distance, but not height... my guess is lowering would reduce distance and make the lower distance settings available unreliable and potentially dangerous if the driver relies upon them.
DCC although not a concern for you, adjustable for dampening, sport, normal and comfort, but to a fixed height spring; again calibrated with tolerances. Shorten the spring and you could literally pop and shock absorber in a pot hole, bumpy ground etc.
Porsche have a very similar system, but both ACC and DCC are height adjustable. The ACC unit moves with height.
Most of the T6's I have seen images of that have been lowered, do not have the ACC unit in the grill and there are plenty of new/used DCC kits on eBay Germany that have been removed by their owners to facilitate lowering.
As a bit of side information, VW also state lowering springs should not be fitted to T6's with the LED lighting option due to calibration issues with automatic range adjustment and the really cleaver bit, MFD adjustment to drive on the right.
So unless VW put the same system on the T6 that is on the Porsche range or an after market company ( there goes the warranty! ) come up with a fix, it's ACC or DCC or both with factory fitted springs or lose the toys and go low.