Sometimes I wonder whether rather than demonstrated the test pilot asses the aircraft ability to handle crosswinds and instead uses a grading from Good to medium good to average to medium poor or poor and not fix an out of the hat number at all
Every time I have flown a flight test to
demonstrate directional control, I have actually flown the aircraft in the 0.2Vso required crosswind, or greater. I could not state that the design requirement continues to be met, if I did not demonstrate that during a flight test. This has involved flights as long as an hour to fly to a runway with proper wind measuring equipment, and the required value for the day. I don't pick the wind speed to be tested to (and the resulting statement for the flight manual supplement, it will be 0.2Vso.
It is not a level of difficulty thing, either I could control the aircraft in that wind, and keep it on the runway with normal use of the flight controls, or I could not - it's pass or fail. If fail (which I have not personally experienced), a change in the rudder might be required. This has been done with Cessna 206, for example, with the installation of certain STOL kits or float kits.
I expect that a pilot who is of average skill on an aircraft, will at least do the aircraft the honour of using full control application if needed to maintain control. So if I can maintain control using full rudder on the runway, I will expect that an average skill pilot will be able to as well! When I was trained in the turbine DC-3, the training pilot specifically instructed me preflight, to roll the control wheel left and right its full travel, just so I was reminded that it goes nearly one whole turn around stop to stop. I expect that he expected me to use full aileron if needed, without being instructed to do so at the moment by him.
I recall only two occasions where I ran out of control during a crosswind landing. One was a Piper Arrow I, and the other the prototype Zenith 701. In both cases, I ran out of aileron on short final, and elected to not continue the landing. Neither was a formal flight test for crosswind capability.
As for test pilot super skill on a type during testing, perhaps some, but not me. Excepting only a C 172, I have never flown a crosswind test on an aircraft type in which I had more than 100 hours total flying experience at the time. Thus, I would rate my skills on that type as "average" for the purpose of that testing. In most cases, I was flying the test with only a couple of hours on type. I'm not offered the luxury of amassing hundreds of hours on a new type before testing it, rather I insist on an hour or two to get familiar (which is usually during more mundane testing anyway).
I do myself the favour of not attempting the crosswind test in very gusty conditions, that is not required for certification, why make it difficult for myself?
I have never flown a plane with "crosswind gear". Any I've known of have either been de-modified, or had the system locked out. I guess that there's a message in that! If it were a good idea, we'd be seeing them in service!