Frost can form on and around cold soaked fuel tanks underneath the wings after high altitude flight . Certainly very common on all the jet types I have flown especially after a rapid descent and it does form in the air not just magically after touchdown!
Should we expect the formation of "frost" on a jet wing, descending from high altitude, to be representative of typical GA flight scenario? I have never flown a jet, and perhaps these conditions can exist in that environment, but I have yet to see "frost" in four decades of flying all kinds of propeller aircraft during Canadian winters.... (I sure have seen ice though
).
I agree that we should not be test pilots with varied or worse prohibited configurations of an aircraft. However, being surprised by a stall shortly after liftoff in a light GA aircraft has me thinking that the pilot was along for the ride, rather than flying the aircraft. If you unstick an aircraft, and it flies to your liking, it should fly better as you allow it to accelerate during the climb away. If, on the other hand, you get it airborne, and then slow it down and stall, you weren't doing it right! If you try to unstick it at the appropriate speed, and it resists your effort, you might consider aborting the takeoff!