Interesting sub-thread Swanlinnet; don't know if the mods will be happy with it here, but, hey-ho.
As a "person who used to be a pilot", you will know that the FAA, CAA and other National Aviation Authorities (under the auspices of the ICAO and Chicago Convention) don't actually teach anyone to fly, although they do regulate such activities. Its difficult to address your submission about the relevance of the Earth's roundness without knowing more about your knowledge base. Yes, the training is broad and intense but, if I remember correctly (1970's for goodness sake!), its not something I remember being taught, or needing, when studying for a PPL, but I think it would certainly have been important if I was to consider long-range navigation, or a commercial licence.
What category of licence did you hold, commercial or private, local or long-haul? Have you ever flown a sector more than a couple of hundred miles? I'd be surprised if you had not learnt, for instance, the need for Great Circle navigation over long distances.