dirkdj
It can't be quite that, because if the rudder has insufficient authority at Vs then the aircraft will go off the runway, at both takeoff and landing.
Also, the side forces on the landing gear can vary over a wide range depending on how long one keeps the aircraft on one wheel after landing; the longer the better.
It's true that it is just a demonstrated figure.
However, the test pilot might have been exceptionally skilled. The TB20 for example has a max demo xw speed of 25kt. I can tell you that you have to be bl**dy good to land it at a real 25kt xw. And I mean real 25kt, not what one usually gets at airfields which is a "25kt" reported xw from an anemometer at the top of a tall pole, with the actual surface wind (at say 2-3ft off the runway) being far less.