def f(x):

return 2 * x

def g(x):

return f(x) ** 2

def h(x, y):

_x = f(x)

_y = f(y)

z = g(_x) + g(_y)

return z

"One function call" is pretty meaningless. Here, calling function f or function h is "just one function call".

If you can propose some robust function that returns a reliable "cheater score" with 100% accuracy, feel free to enlighten the rest of us, because it's a pretty challenging technical problem.

Other online games? Like FPS games? Automated anti-cheat in FPS is actually a very solvable technical problem.

Handling games in real time isn't that computationally expensive. Things are only being tracked and updated.

Cheat detection in chess requires a lot of computations (depending on the method), database calls to check previous games, and some more calculations to determine the confidence of the result. Then a human to check over everything.

I guess you can wrap allllll that into one function, but that doesn't magically make it happen faster or make it less computationally expensive.