Vertical Justification?

In Layout Option, does the setting “Justify staves when frames with single system is above this threshold” mean that if it’s turned off, a single system is not justified?

That’s what I think it means, but that’s not what I’m getting: I’ve turned it off, and I’m still getting single systems justified. I want frames with more than one system justified, but not frames with just one.

That option determines whether Dorico should use the staff justification value even when the system is only sufficiently full for system justification, if there’s only a single system in the frame.