Yes, that's how it's typically measured, but of course it is dependent on saddle design, which messes it up as an accurate measurement unless you are comparing identical saddles.

I did one on-line bike fit (don't remember which) and it suggests 11-12cm setback - just seemed crazy (and impossible to achieve on my bike), so I ignored it.

I would say 6-8cm is probably normal for my inseam (c. 87cm / 34"), even though the LeMond table I saw suggested 4-6cm. UCI limit is 5cm I understand, shorter riders would have a problem with LeMond's measurements.