Does not matter. The distance to the horizon formula works in its prediction. Also why are there 24 time zones? How come by knowing the time precisely you can tell what your longitude is? Why is the Earth's shadow on the Moon always circular? All the Objects big enough to be a planet are spheres, why would Earth be any different?
In approximately 240 BCE, the Greek scholar Eratosthenes calculated the circumference of the Earth to be about 25,000 miles a figure remarkably close to the modern measurement. Do you actually believe in a flat Earth or do you just enjoy yanking people's chain?