The example I was thinking specifically about and can be used as an example.
We were descending in FLCH, can't remember the speed but let's say it was 280 kts. In the descent, and long before we reached our cleared level, we were given further descent with a minimum of 2500 fpm. The plane has now been descending on idle power in throttle hold. When V/S is selected A/T wakes up and advances the thrust to c.a. 1.05 EPR. At the same time, as we are doing a good rate down, the speed of course starts to increase above bug speed (280 Kts).
This is just one of many examples when the V/S mode increases speed, and I'm not talking about when the A/T increases thrust to maintain speed. As in the situtation above we were already above the bugged speed so no need for extra thrust.
Just wondering about the system logic behind it.