> I don't think your average centrist knows what that it
I think you're illustrating exactly the point that was aimed for – everyone defines these vague concepts relative to their own perception. Even what is "center" is probably bound to vary wildly depending on ones own perspective.
On any given line segment, the center is fixed. It's only perceptions of it that vary wildly.
What's also does vary is people's definition of the line segment, both directionally (what do liberal and conservative actually mean?), and where it starts and ends.
When I define the start and end, I'm typically not talking about centrism in SF, or globally. I'm talking about centrism in the USA. I realize not everyone here is American, but that may provide context for my statement.
I think you're illustrating exactly the point that was aimed for – everyone defines these vague concepts relative to their own perception. Even what is "center" is probably bound to vary wildly depending on ones own perspective.