[dontreact]

I don't follow this. The answer contained in the link seems more relevant as it has to do with the fact that the harmonics of real metal strings are not ideal and so the detuning at both ends compensates for this.

It seems like you are talking about what would happen if you tuned a piano using something other than equal temperament. Why is the iterated fifths relevant at all in this case?

[jedimastert]

Generally, Pythagorean tuning uses perfect fifths, as it's the easiest to hear and to match using harmonics. That example is just showing that if you using consecutive intervals (such as fifths) then other intervals (such as octaves and thirds) won't line up.