When the "flimsy" was in use it had no ability to mount a spout and required a funnel. Expedient funnels and hoppers were made and distributed by REME in the Western desert to speed up the fuelling of vehicles and aircraft. A properly "engineered" hopper was designed in Britain just as the "Jerry can' was being copied by the Brits. The hopper was then suitably over-engineered to accept the "Flimsy" pol can and the new "Jerry Can".
There is nothing wrong with British engineering in fact, the British love engineering.