For whatever it's worth, it's notable that with the 109K and 190D9 would both consume all of their fuel before their MW50 at the low flow rate (MW50 systems on the 109 had two flow rates, presumably this would be similar on the D9).
I'm unsure which flow rate is modeled in the game. Perhaps the extended WEP duration on the 109 and 190 is intended to reflect this easily without somebody having to do math.
Additionally, with 2x fuel burn (and normal MW50 usage), fuel would be consumed first even at the high rate of flow.