Actually, I'm pretty certain the test pilots do use techniques to compensate for the crosswind when getting the 'max demonstrated' crosswind figure. There's little point in demonstrating the maximum sideload that the undercarriage can take when it can be calculated in the design office. The test is one of the handling of the aircraft rather than just the strength of the gear.
I'm sure G will be along momentarily to fill us in more fully though. He knows all about this kind of thing.