*sigh*
The usual amateurs come out of the woodwork again. (Not you, JT)
The certification process for the average light aircraft did not require it to be tested on crosswind landings until it breaks. The certification process merely required a demonstrated crosswind number that didm't break the aircraft. Any number will do. Provided it's a demonstrated number, that's good enough from a certification perspective.
I do laugh at those who seem to be suggesting that the certification basis for aircraft that have been around for decades is ascertainable against contemporary test guidance.