Tree:
That is not true of the 6 different aircraft types I have operated
(Lockheed, Boeing, Airbus) In my experience any prolonged exposure to a SAT of -60 or more has caused fuel temps well below -37C and required a modification to the flight envelope. The small Airbus models are especially affected.
Jet A1 will freeze at -47 C. Considering the amount of fuel 777 was carrying SAT -60 is not cold enough to freeze it on the way from PEK to LHR. In the NW parts of Russia SAT has been around -70 (~FL390) lately, but even that is not cold enough. I have been flying (A340) many times in temperatures like -76 SAT and even in that temperature it takes hours before fuel temp in outer tanks (wing tip) drop below -40. In inner tanks temperatures are then still well over -40 deg.