Of course, the chances that in real life a custom object will have hash == -2 are very small. Different story however is for the actual numbers -1 and -2:

In [2]: %timeit {-1, -3}                                                                                                                                                                                                        
64.2 ns ± 1.41 ns per loop (mean ± std. dev. of 7 runs, 10000000 loops each)

In [3]: %timeit {-1, -2}                                                                                                                                                                                                        
238 ns ± 5.64 ns per loop (mean ± std. dev. of 7 runs, 1000000 loops each)