In my time as a commercial pilot I have flown with a few former military test pilots, one from ETPS (Empire Test Pilot School) and the others from equally respectable foreign equivalents, EPNER of France being one. What marked these exceptional pilots out was their humility and complete acceptance of their own potential to make omissions and mistakes. Apart from their handling skills, high IQs and scientific proficiencies, which might have led others to believe that they were "SkyGods", they exhibited remarkable humility.
Having been "put through the wringer" in the simulator at least every 6 months for some decades and flown with outstandingly capable colleagues in all weathers, I can vouch that none of them and least of all the test pilots would ever advocate flying IMC without the autopilot engaged in rough weather. We would all be relaxed enough to hand-fly on instruments for practice in benign conditions, including the ILS down to 500' QFE or lower, but only if there wasn't some distracting problem to deal with.