The idea is to be able to simply deactivate any active state for a button bar which a checkbox or pulldown.
Active state can be useful, but sometimes it can just get in the way.
Right now "None" in active button bar doesn't do this, it just has not of the button's be active until one is clicked. You can use the "Specify..." option and set the calculation o double quotes to basically remove the active state from a button bar, but it would nice to just have a checkbox that says "No active state", or make that an option in the pulldown.
Sometimes you just don't want an active state but want the other cool features of a button bar. For example the active state will override the hover state, so even if you style your active state to look like inactive, you're going to lose your hover. Also, PORTALS. The button bar segment becomes active on EVERY LINE? REALLY? That's a bug not a feature. Please fix that as well.
I would also say the default should be having the no active state checkbox checked, but I would be curious how other developers use it. I almost never use it.