Bike fit / correct riding position

I think what hippy and I are pointing out (since you are referring to what the point is or isn't) is that your generalisations are simply too... generalised to be useful.

Exactly. Generalisations are good if estimating bike fit. But as you actually have the person, the bike and a tape measure you can use true measurements rather than estimates based on averages.
Unless you happen to know you fit dead centre of the bell curve in which case you can just ask for a bike that fits a 178cm person and the shop keeper will go out back and get you one.