You make a good point.
If you look at the labels on the axis; you’ll see that it’s really a “social authoritarian — social libertarian” scale. That’s a more narrow focus, than a scale measuring the extent that governments use coercive force on its citizens. It does leave out use of force to (say) redistribute property.
I was originally going to comment on the on-line tests, such as the one that Sopater mentioned above. That test also rates you on a “social authoritarian — social libertarian” scale.
You could construct many different models of the political realm — as I said before, none of them would be perfect. However, it’s likely that a 2D model is better than a 1D model.
Your libinlaw might just not want such an “in your face” display of what government coercive force looks like. Like an anti-hunting urbanite, who buys meat at the supermarket — she wants her socialism; but, she doesn’t want to know where it came from.
Yeah, most libs like “social policy” that makes them feel good about themselves,
but, in my example, they’ll deny that they are advocating sticking a gun in the face of those that are being forced to pay for “their” act of beneficence.
When you try to logically walk them through the process, they get to the point where they virtually or literally stick their fingers in their ears and sing “la la la la”.