(dontfeedthetrolldontfeedthetrolldont.. ah, damnit!)
The torque converter is usually always engaged, always wants to go, while holding the brake. As soon as the brakes are released the car starts rolling forward.
With the VW T4 that didn't work as on other cars since the torque converter was disengaged while stopping.
So the driver had to change to the accelerator more quickly than usual, if starting uphill.
Otherwise, since the torque converter engaged only a second after releasing the brake, the car would roll approximately 5cm backwards before going forward. (If starting without any accelerator input.)