Wait. Is it a myth, or are you saying that it's a myth? Clarify your statements.
The Coriolis force is a well known myth. The direction of the wind is not dependent on the shape of the earth, but the shape of the land, local temperature, pressure gradients, entropy, humidity levels, and gas constant.
Round Earth:
Distance between Perth and Tokyo: 7894Km (Trip @ ~800Km/h: 10 Hours)
Distance between Perth and Sydney: 3307Km (Trip @ ~800Km/h: 4 Hours)
Your Map:
Perth and Tokyo: 98 pixels
Perth and Sydney: 37 Pixels
Explain.
The fallacy is that you're assuming planes travel directly between two distant points. In reality they hop around a lot between destinations, refueling, and picking up and dropping off passengers. It would be extremely hard to gauge actual travel time doing that.
You are also neglecting how jetstreams and wind conditions can alter a flight's time. Additionally, if the flat earth is rotating, that's another variable to consider when traveling between hemidisks.
Have you ever been to an airport? It seems as if every other incoming flight is delayed for some reason or another. Inaccurate maps may very well be one of those reasons.