The term "freezing point" for Jet-A1 is maybe somewhat misleading. It's basically the temperature below where the normally "transparent" fuel shows its first traces of "milkiness". Diesel guys refer to this as the Cloud Point. The flow is not impaired at this temperature.
Further... The Fuel Temp warning on the 777 has a triggerpoint 3degC higher than the temperature set by the crew (via the CDU).
This also increases the likelihood that freezing will be detected before it starts to cause a problem.