
Robert,
I think I recall something about this coming up before. I tested just now in a game and observed the same thing. I duplicated your Inspiring Boost and found it. I also created a new test ability with nothing but the name filled out, and it triggered the dice roll when pushed.
If I recall correctly, the 3d dice 'listen' for a button to be pushed. If part of that button tells them to roll dice, they roll those dice. If it doesn't, then they just roll some d20s. You can turn 3d dice off and they won't do that. In my testing, the number posted with the ability was not affected by the dice on the screen. I tried some variations of putting 'dummy' dice in other fields but it didn't stop the d20s.