alosaurus … aah de Havilland. May have flown with you during guest appearances at Chester.
IIRC the 125 fuel flow meter had a peculiarity associated with the engine where a small ‘leak path’ fuel-flow was not registered as it by passed the main burner flow where the detector was located. I can no longer recall the purpose of the bypass, but at the time it seemed to be an important engine design feature, but a nuisance when determining accurate fuel usage.
I haven’t seen this feature on other engines, but that’s not to say some don’t have similar problems; otherwise my experience suggests that the fuel gauging and flow meter accuracies are similar.