MSOCS,
Yes, the issue is designers "hiding" the weight of the cooling medium within the fuel load.
You saying "the min landing fuel for F-35B is well established now. Temp isn't a factor in practice" implies that it IS a factor and, there is a considerable temp related min fuel limitation, ie the jet has to carry around deadweight fuel for the whole mission.
What is it? 500Kg?
Like I said, if the cooling was augmented with a consumable coolant at less overall system weight than the landing fuel penalty, that would be a big bonus.
As I don't know the F-35 system details, I cannot be more specific.
BTW, the mission environment had better allow for 50 degree Centigrade surface level temps and, in those climate conditions, you cannot rely on cool fuel from tankers either. Sitting on the apron, tanker fuel temps can get OOL for their own operation!
OAP