I am basically a lurker, but I've read the thread fully, and see a loophole for stoic. The FOHE is not labelled as a filter, filtering is simply not its intended function. Nominally, its blockage was caused by trapping ice at the tube sheet. There is even a bypass, but for the oil, not the fuel, and that through an air cooled matrix.
Technically, it did 'filter' the fuel. Additionally, it is not intended as a fuel heater, but does that as well, though 'poorly'.
with respect,
bear