It works for normal monsters. Mini bosses are included in MVPs as well. There are certain monsters also with miniboss technicalities that ignore vacuum such as necromancers and anubis, even though they are technically not minibosses. They are still classified in the group known as mini bosses. Kasas and salamanders included. Anything such as Imps or abbey 2, will be affected by vacuum extreme.
This is the way kro has set it and so has eAthena. We are currently extremely up to date and this setting is part of it. It was also stated in my changelog, in beta, there was a fix for vacuum extreme applied to the duration of the skill. The duratin now lasts the length of time as the animation effect instead of being triple what it was supposed to be.