Such maths used to prove flatness of the Universe in our 3 dimensional Universe may merely be a hypothesis, remember - it is admittedly based upon probabilities. Furthermore, it is still an assumption & another belief in the POSSIBILITY of the UNKNOWN yet that would lead to a paradigm shift.
No doubt we Humankind had advanced from the stone age, I would readily agree that we STILL have much to know & learn, as for sure, we are not masters of the Universe....
Let's do a test on "perceptions'.
A)If the Universe or our planet is Flat, then everything would be in 2 dimensional. So what about a HDB block of flat? Does it look 2 dimensional, of only length & breadth, let alone even the Human figure?
Flat earthers would argue that their beliefs is not about structures & beings, but only the planet is flat. Thus, their own beliefs which claims to be of science, is debunked by their own words - it's either a 2 dimensional World where EVERYTHING is 2 dimensional, & nothing is in 3d.
Then there is the arguments about different dimensions type of Worlds. Such exists only in Quantum physics in theoretical forms, but none had successfully created or seen such dimensions. To argue that such exists is based upon beliefs, & not science.
B)When Humankind looks up at the skies, they can see the sun, moon, stars, etc. They are certainly not 2 dimensional but flat earthers will claimed that Humanity had never gone to the moon & the space program was a hoax. Such presumptions can be acceptable, as most had not gone to the stars...
However, take for instance - meteorites. These are parts of other world objects that fell to Earth, proven with evidences & science based upon their atomic & molecular structures, which are not from Earth.
Such objects have length, breath & height, mass & volume. Such objects alone PROVES that the universe is NOT flat, & any mathematical models used, more so based upon probabilities, had been done in error & are merely hypothesis, NOT FACTS.